Polyuronic acid derivative and aqueous ink composition polyuronic acid derivative

ABSTRACT

A self-dispersed pigment ink composition is provided which gives reliable printing performance and yields printed images that have excellent print quality and a dispersant which can realize the ink composition. New polyuronic acid derivatives, as a dispersant, according to the present invention characterized in that polyuronic acids are attached by reductively amination, through reducing termini of the polyuronic acids, to glyceryl poly(oxypropylene) triamine.

TECHNICAL FIELD

This invention relates to a new polyuronic acid derivative and an inkcomposition comprising the polyuronic acid derivative as a dispersant oran additional polymer, especially for use in an ink jet printing method.

BACKGROUND ART

Ink jet printing is a non-impact printing process in which the printerproduces droplets of ink in response to digital signals, such as thosegenerated by a computer. The droplets of ink are deposited on asubstrate such as paper or transparent films. Ink jet printers havefound broad commercial acceptance due to their print quality, low cost,relatively quiet operation, and graphics capability.

The inks used in ink jet printers can be classified as either dye-basedinks or pigment-based inks. Dye-based inks are satisfactory for mostapplications, but generally have poor light fastness and waterresistance. As a printed document is expected to have a certain degreeof permanency, the lack of light fastness and water resistance of theprinted image derived from dye-based inks is a problem. Pigment-basedinks can be prepared which have excellent light fastness and waterresistance. Thus, for purposes of obtaining a printed document with areasonable degree of permanency, pigment-based inks are preferred overdye-based inks.

A great concern with ink jet printing is the level of print quality, asdefined by edge acuity or sharpness of an image and minimal feathering,which can be obtained on “plain paper.” In recent years there has beenan increasing demand for ink jet printers that provide excellent printquality on plain paper. The present invention is mainly concerned withprint quality as defined by edge acuity or sharpness of the printedimages on plain paper. In terms of print quality on plain paper,suitably designed pigment-based inks are especially desired.

When a liquid ink droplet contacts the paper surface as a result of inkjet printing, the liquid spreads out from the impact origin andpenetrates the paper. Cellulose fibers, present in most plain papers,tend to act as wicks that draw the liquid along the length of theindividual fibers by capillary action. In dye-based inks, in which thecolorant is homogeneously dissolved in the liquid, the colorant willspread out, penetrate, and be drawn along the length of cellulose fibersto the exact same degree as the liquid. The typical result for adye-based ink is a colored dot that has poorly defined feathered edges.

In pigment-based inks, in which the colorant is homogeneously dispersedin the liquid, unless the dispersion stability of the colorant isdisrupted upon contact with the paper, the colorant will spread out,penetrate, and be drawn along the length of cellulose fibers to thenearly the same degree as the liquid. The typical result for aconventional pigment-based ink is a colored dot that has poorly definedfeathered edges.

In contrast, a suitably designed pigment-based ink, in which thedispersion stability of the colorant is disrupted upon contact with thepaper, the colorant will not spread out, penetrate, and be drawn alongthe length of cellulose fibers in the same way as the liquid. For thistype of ink, the colorant effectively separates from the liquid carrier.The result is a colored dot that has a sharp edge boundary withnegligible feathering.

Water-based pigment dispersants are well known in the art, and have beenused commercially for applying films, such as paints, to varioussubstrates. A dispersant using a polyuronic acid is also suggested. Forexample, in U.S. Pat. No. 6,242,529, a polyuronic acid derivative inwhich a hydrophobic polymer is covalently attached to the reducingterminus of the polyuronic acid is disclosed as a dispersant. Thesehydrophobic polymers include photopolymers or copolymers prepared fromat least one monomer selected from the group consisting of styrene orsubstituted styrenes, vinyl pyridine or substituted pyridines,methacrylic acid esters, acrylic acid esters, acrylonitrile,methacrylonitrile, butadiene, and isoprene. The hydrophobic polymersalso include poly(dimethylsiloxane), hydrophobic polyamides, andhydrophobic polyamines.

On the other hand, one general approach for obtaining reliable aqueouspigment-based inks is to use self-dispersed pigments in the inkformulations. As the descriptive phrase, “self-dispersed,” is commonlyused, these pigments do not require dispersing agents, such as polymericdispersants or surfactants to produce stable dispersions of the pigmentin the aqueous vehicle. The means by which the pigments areself-dispersed is the deliberate introduction onto the surface of thepigment particles of a sufficient number of charged functionalities.This approach has been widely applied to black pigments derived fromcarbon black.

With regard to print quality on plain paper, aqueous pigment-based inksthat use self-dispersed pigments in the ink formulations areadvantageous. Specifically, the print-quality advantage arises from thefact that inks can be formulated with relatively high pigment contentswhen self-dispersed pigments are used. High pigment contents generallytranslate into high optical densities when the inks are printed on plainpaper. As noted above, high optical densities typically result in imagesthat are preferred by consumers in comparison with images with loweroptical densities that are perceived as “dull.”

When printing by using aqueous pigment-based inks comprisingself-dispersed pigments, however, they yield images with exceptionallypoor lustrousness and exceptionally poor adhesion on coated specialtymedia. These failings are generally attributed to the non-inclusion ofpolymeric dispersing agents in the ink. Polymeric dispersing agents,which typically are resinous and partially bonded to the pigmentsurfaces, act as both a glaze for smoothing out the rough surface of thepigment and as a binder for mediating adhesion between pigment particlesand adhesion between pigment particles and the surface of the specialtymedia.

A simple and obvious approach to overcoming the adhesion deficiency ofinks that use self-dispersed pigments is to add a resinous polymericbinder to the ink composition. The inclusion of the resinous binder,which can function as a glaze, also improves the lustrousness of theprinted images on coated specialty media in comparison to those imagesderived from unadulterated self-dispersed pigment formulations. As faras the present inventers know, the self-dispersed pigment/bindercombinations may fall considerably short of the adhesion andlustrousness that is achieved routinely using non-self-dispersed pigmentdispersions, in which a dispersing agent is required to produce a stabledispersion.

There is a demand for pigment dispersed aqueous ink compositions thatgive reliable printing performance and yield is printed images havingexcellent print quality.

Further, there remains a demand for self-dispersed pigment aqueous inkcompositions that give reliable printing performance and yield excellentprint quality, specifically on plain paper.

Furthermore, there is a demand for self-dispersed pigment aqueous inkcompositions that yield excellent print quality on coated specialtymedia that exhibit lustrousness. In particular, there remains a demandfor self-dispersed pigment aqueous ink compositions that yield printquality on coated specialty media such that good lustrousness and goodadhesion are obtained.

SUMMARY OF THE INVENTION

The present inventors have now found that a certain kind of newpolyuronic acid derivatives are excellent as a dispersant and anadditional polymer. The present invention has been made based on suchfindings.

Accordingly, it is an object of the present invention to provide apigment dispersed aqueous ink composition which gives reliable printingperformance and yields printed images that have excellent print quality,especially on plain paper, and a dispersant which can realize the inkcomposition.

Furthermore, it is an object of the present invention to provide aself-dispersed pigment aqueous ink composition which gives reliableprinting performance and yields printed images that have excellent printquality, especially excellent lustrousness and fixation for printing onboth plain paper and coated specialty media.

According to the present invention, there is provided a new polyuronicacid derivative comprising glyceryl poly(oxypropylene) triamine andpolyuronic acids which are attached by reductively amination, throughreducing termini of the polyuronic acids, to the glycerylpoly(oxypropylene) triamine.

According to the first preferred aspect of the present invention, thereis provided the polyuronic acid derivative wherein one polyuronic acidis attached by reductively amination, through a reducing terminus of thepolyuronic acid, to the glyceryl poly(oxypropylene) triamine which isrepresented by the general formula:

wherein the average value of the sum, x+y+z, is greater than or equal to10 and less than or equal to 150, more preferably greater than or equalto 10 and less than or equal to 100.

According to the second preferred aspect of the present invention, thereis provided the polyuronic acid derivative wherein two to six polyuronicacids are attached by reductively amination, through reducing termini ofthe polyuronic acid, to the glyceryl poly(oxypropylene) triamine whichis represented by the general formula:

wherein the average value of the sum, x+y+z, is greater than or equal to30 and less than or equal to 250, more preferably greater than or equalto 10 and less than or equal to 120.

Further, according to the present invention, there is provided anaqueous ink composition comprising water as the principal solvent, aself-dispersed pigment, and the polyuronic acid derivative descriedabove.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Polyuronic Acid Derivatives

New polyuronic acid derivatives according to the present invention arecomposed of two parts: a hydrophilic polyuronic acid segment and ahydrophobic polymer segment derived from a glyceryl poly(oxypropylene)triamine.

The polyuronic acid derivative according to the present inventionfunctions as a dispersant for dispersing pigments in ink compositions.The resulting pigment dispersed aqueous ink composition gives reliableprinting performance and yields printed images that have excellent printquality, especially on plain paper. Although the reason for this has notbeen fully elucidated yet, it is believed that the polyuronic acidderivative of the present invention, which contains a hydrophobicsegment and a hydrophilic segment, functions better than conventionaltwo-part type dispersants. It yields stable dispersed pigments fromwhich printed images, which are free of feathering, are realized. Thehydrophobic segment of the derivative adheres to the surface of thepigment such that the pigment is dispersed effectively in the inkcomposition. Furthermore, the polyuronic acid segment of the derivativehas a structure containing up-down alternating pockets lined withcarboxy groups and hydroxyl groups that are just the right size forbinding multivalent cations, especially dipositive calcium ions. Whenthe polyuronic acid segment of the polyuronic acid derivative binds tomultivalent cations, which are present on the surfaces of typical plainpapers, the stability of the pigment dispersion is disrupted. Thisinhibits the pigment colorant from spreading out on the paper such thatprinted images, which are free of feathering, are realized.

<Polyuronic Acid Segment>

The polyuronic acid is selected from the group of polyuronic acidsconsisting of either 1,4-linked poly-(α-D-galacturonic acid) or1,4-linked poly-(α-L-guluronic acid). These polyuronic acids areavailable from natural materials and may also contain small amounts ofother uronic acid saccharides and/or non-uronic acid saccharides. In1,4-linked poly-(α-D-galacturonic acid) the impurity component isgenerally the non-uronic acid saccharide, rhamnose. In 1,4-linkedpoly-(α-L-guluronic acid) the impurity component is generally the uronicacid saccharide, mannuronic acid. The D-galacturonic acid content of the1,4-linked poly-(α-D-galacturonic acid) used in this invention isgreater than 85% wt. %. More preferably the D-galacturonic acid contentis greater than 90 wt. %. Even more preferably the D-galacturonic acidcontent is greater than 95 wt. %. The L-guluronic acid content of the1,4-linked poly-(α-L-guluronic acid) used in this invention is greaterthan 80% wt. % More preferably the L-guluronic acid content is greaterthan 85 wt. %. Even more preferably the L-guluronic acid content isgreater than 90 wt. %.

1,4-linked poly-(α-D-galacturonic acid) is obtained by de-esterificationand hydrolysis of pectin, a naturally occurring hydrocolloid which isobtained from fruits such as lemons, limes, grapefruits, oranges,mangoes, apples, sunflowers, and sugar beets. The highly water-soluble1,4-linked poly-(α-D-galacturonic acid) product can be isolated from thehydrolysis reaction solution by (1) evaporation of the solvent, (2)precipitation induced by the addition of a poor solvent for the product,or a combination of (1) and (2). 1,4-linked poly-(α-L-guluronic acid) isobtained by partial acid hydrolysis of alginic acid, a naturallyoccurring polysaccharide obtained from seaweeds such as giant kelp(Macrocystis pyrifera), horsetail kelp (Laminaria digitata), and sugarkelp (Laminaria saccharina), followed by selective precipitation.Selective precipitation may be carried out by the controlled addition ofacetic acid to an aqueous solution of the 1,4-linked poly-(α-L-guluronicacid) product.

The number average molecular weight of the polyuronic acid used in thepresent invention is greater than or equal to about 700 and less than orequal to 15,000, more preferably greater than or equal to about 700 andless than or equal to about 10,000.

<Hydrophobic Polymer Segment>

The hydrophobic polymer segment is that derived from a glycerylpoly(oxypropylene) triamine represented by the general formula:

wherein, in the polyuronic acid derivative according to the firstembodiment of the present invention, the average value of the sum,x+y+z, is greater than or equal to 10 and less than or equal to 150,more preferably greater than or equal to 10 and less than or equal to100.

Further, in the polyuronic acid derivative according to the secondembodiment of the present invention, the average value of the sum,x+y+z, is greater than or equal to 30 and less than or equal to 250,more preferably greater than or equal to 30 and less than or equal to120.

Glyceryl poly(oxypropylene) triamines are commercially available fromHuntsman Corporation (Performance Chemicals Division; Houston, Tex.,USA). These compounds are used as highly reactive soft blocks inpolyurea RIM and spray applications. They also have uses asthermoplastic modifiers and as adhesion promoters in epoxy systems. Theyalso have uses as modifiers and as curatives in polyurethane elastomersand foams. At the present time, Huntsman Corporation has glycerylpoly(oxypropylene) triamines available in two different averagemolecular weight distributions, Jeffamine XJT-509 and Jeffamine T-5000.The former has an average molecular weight of approximately 3000 with anaverage sum, x+y+z, equal to about 50. The latter has an averagemolecular weight of approximately 5000 with an average sum, x+y+z, equalto about 80. Both Jeffamine XJT-509 and Jeffamine T-5000 are insolublein water as is expected for hydrophobic polymers. On the other hand,they are quite soluble in alcoholic solvents.

In the polyuronic acid derivative according to the first embodiment ofthe present invention, as the sum, x+y+z, approaches the lower limit of10, these glyceryl poly(oxypropylene) triamines are expected to becomeonly slightly soluble in water.

Further, in the polyuronic acid derivative according to the secondembodiment of the present invention, even as the sum, x+y+z, approachesthe lower limit of 30, these glyceryl poly(oxypropylene) triamines arenot expected to be soluble in water.

Polyuronic Acid Derivative According to the First Embodiment of thePresent Invention

Polyuronic acid derivative according to the present invention is thatpolyuronic acids are attached by reductively amination, through reducingtermini of the polyuronic acids, to glyceryl poly(oxypropylene)triamine.

There are several important considerations with regard to the covalentattachment by reductive amination that are described below.

As to the first consideration, in order to attach only one polyuronicacid molecule per glyceryl poly(oxypropylene) triamine molecule, it isnecessary to use at least a three-fold molar excess of the triamine withrespect to the polyuronic acid. The triamine has three reactive amines,two associated with the poly(oxypropylene) branches attached to theterminal hydroxyl oxygen atoms of the glyceryl unit and one associatedwith the poly(oxypropylene) branch attached to the central hydroxyloxygen atom of the same glyceryl unit. Preferably, a solution of thepolyuronic acid starting material is added to a solution containing atleast a fivefold molar excess of the glyceryl poly(oxypropylene)triamine starting material. Arising by-product is practicallyunavoidable because the by-product is produced when a small amount ofpolyuronic-acid doubly attaches to a single glyceryl poly(oxypropylene)triamine. Therefore, the mixture containing this by-product is includedwithin the scope of the present invention.

As to the second consideration, in attaching one polyuronic acidmolecule per glyceryl poly(oxypropylene) triamine molecule, it is thatthe product obtained is a complex mixture, even if the small unavoidableby-product described in the above section is ignored. First, thepolyuronic acid starting material is a complex mixture of polyuronicacid molecules having a relatively broad range of degrees ofpolymerization. Theoretically one could use expensive and time-consumingseparation methods on the polyuronic acid starting material in order toobtain pure fractions containing polyuronic acid molecules of the exactsame degree of polymerization. However, such fractionation is neithereconomically practical nor necessary from the standpoint of theperformance of the dispersant product. Second, the glycerylpoly(oxypropylene) triamine starting material also is a complex mixtureof glyceryl poly(oxypropylene) triamine molecules with a relativelybroad range for the total count of propylene oxide units. Furthermore,the distribution of propylene oxide units among the three glycerylhydroxyls varies considerably. Third, the combination of a broaddistribution of polyuronic acid molecules with a broad distribution ofglyceryl poly(oxypropylene) triamine molecules results in an evenbroader distribution of product molecules being formed. Fourth, even ifboth the starting materials were structurally pure fractions, thecombination of one polyuronic acid and one glyceryl poly(oxypropylene)triamine, under practical reaction conditions, will result in a mixtureof three isomers: about one-third statistically will consist of onepolyuronic acid bound to one of the two poly(oxypropylene) branchesattached to the terminal hydroxyl oxygen atoms of the glyceryl unit,about one-third statistically will consist of one polyuronic acid boundto the other of the two poly(oxypropylene) branches attached to theterminal hydroxyl oxygen atoms of the glyceryl unit, and about one-thirdstatistically will consist of one polyuronic acid bound to thepoly(oxypropylene) branch attached to the central hydroxyl oxygen atomof the glyceryl unit. Considering this positional isomerism, thetri-positional combination of a broad distribution of polyuronic acidmolecules with a broad distribution of glyceryl poly(oxypropylene)triamine molecules results in an even broader distribution of productmolecules than envisioned in the absence of the positional isomerism. Inany case, it is neither economically practical nor typical necessaryfrom the standpoint of the performance of the dispersant product to tryand separate the dispersant product into structurally pure fractions.

As to the third consideration, in attaching one polyuronic acid moleculeper glyceryl poly(oxypropylene) triamine molecule, although it is notabsolutely necessary, it is extremely desirable to effect the reactionof the two reactants in a homogeneous solution. Homogeneous conditionsfor the initial combination of the two reactants are desirable forachieving the conditions in which the glyceryl poly(oxypropylene)triamine is in a molar excess with respect to the polyuronic acid.Heterogeneous mixtures have mass-transfer limitations that makeachievement of the molar excess condition difficult on the molecularscale. In other words, even if a huge excess of the glycerylpoly(oxypropylene) triamine is present, rate of transfer of one reactantto a different phase which contains the other reactant is limited by thesurface area of the interfacial region between the reactants. In theworst-case scenario, (1) glyceryl poly(oxypropylene) triamine istransferred to the phase containing the polyuronic acid component inpreference to the reverse transfer and (2) the combination of thereactants is fast with respect to the phase-to-phase transfer. In thisscenario, with phase-to-phase transfer being rate limiting, aftertransfer of one molecule of the poly(oxypropylene) triamine to thepolyuronic acid containing phase, three molecules of polyuronic acidhave a high probability of combining with one molecule of thepoly(oxypropylene) triamine. This is counter to the intent with whichone uses an excess of the glyceryl poly(oxypropylene) triamine reactant.

Thus, as to this third consideration, it is extremely desirable to carryout the reductive amination reaction in a homogeneous solution. Becausethe polyuronic acid component is very hydrophilic and the glycerylpoly(oxypropylene) triamine component is by design hydrophobic, findinga compatible solvent medium is potentially problematic. Nevertheless theinventor of the present invention has found that slow addition of anaqueous solution or slurry of the polyuronic acid to a methanol solutioncontaining the glyceryl poly(oxypropylene) triamine and a small amountof water results in the formation of a homogeneous solution. Some of themethanol may be replaced with higher alcohols including ethanol,n-propanol, and isopropanol without disrupting the homogeneity of thefinal mixture, Methanol, however, appears to be an essential component.

Polyuronic Acid Derivatives According to the Second Embodiment of thePresent Invention

The polyuronic acid derivative according to the second embodiment of thepresent invention is that two to six polyuronic acids are covalentlyattached by reductively amination, through reducing termini of thepolyuronic acid, to glyceryl poly(oxypropylene) triamine

As is similar to the polyuronic acid according to the first embodimentof the present invention or it adds to that, there are several importantconsiderations with regard to this type of covalent attachment byreductively amination as described below.

As to the first consideration, it is that both the glycerylpoly(oxypropylene) triamine and the polyuronic acid starting materialsare complex mixtures of molecules. For the glyceryl poly(oxypropylene)triamine, the primary element of complexity is the total number ofpropylene oxide units per molecule. Typically an approximately Gaussiandistribution centered around a peak value is observed. A secondaryelement of complexity, for a given fixed total number of propylene oxideunits, is the distribution of the numbers of propylene oxide units amongthe three poly(oxypropylene) chains, which extend from the threestructurally different glyceryl hydroxyls. For the polyuronic acid, theonly element of complexity is the total number of uronic acid units permolecule, if impurity saccharides are ignored. Within thisspecification, for purposes of simplification, the poly(oxypropylene)triamine and the polyuronic acid starting materials are treated asaverage structures with average molecular weights. Nevertheless, onemust not forget that one is combining complex mixtures. That is, forextreme combinations, such as (1) a high degree of polymerizationtriamine with polyuronic acids having low degrees of polymerization or(2) a low degree of polymerization triamine with polyuronic acids havinghigh degrees of polymerization, the resulting products may havecharacteristics which differ significantly from that of the “average”product resulting from a combination of two “average” startingmaterials. However, as long as the extreme combinations function asnegligible components of the product mixtures, they can be ignored forpurposes of discussion.

It follows from the above discussion that the product dispersant of thepresent invention will by necessity be a complex mixture. Theoreticallyone could use expensive and time-consuming separation methods on boththe starting materials in order to obtain pure fractions and then carryout additional expensive and time-consuming separation methods on theproduct in order to obtain pure fractions. Such fractionation is neithereconomically practical nor necessary from the standpoint of theperformance of the dispersant product.

From the standpoint of the aqueous solubility of the dispersant product,the necessity for attaching two or more polyuronic acids per glycerylpoly(oxypropylene) triamine molecule is manifested when the solvatingpower of only one covalently attached polyuronic acid is insufficient tosolubilize the one-to-one product. Two extreme cases can be considered:(1) the average molecular weight of the polyuronic acid startingmaterial is relatively small and (2) the average molecular weight of theglyceryl poly(oxypropylene) triamine is relatively large. For polyuronicacids with number average molecular weights at or near the lower rangeof the present invention specification, aqueous solubility of theone-to-one product is not expected. Similarly, for glycerylpoly(oxypropylene) triamines at the higher end of the range, such asJeffamine T-5000 with an average sum, x+y+z, equal to about 80, theinventor of the present invention has found that two or more polyuronicacids must be covalently attached to the triamine in order to obtainaqueous solubility. Although in theory a maximum of six polyuronic acidscan be covalently attached by reductive amination to a single glycerylpoly(oxypropylene) triamine, the preferred level of covalent attachmentfor the present invention is two. This level of double attachment leavesone of the three original primary amines unmodified such that it is freeto facilitate adsorption of the hydrophobic portion of the dispersantonto the surface of the pigment particle.

A very important consideration for realizing the covalent attachment oftwo or more polyuronic acids to a single glyceryl poly(oxypropylene)triamine is that the reaction preferably carried out under homogeneousconditions. Because the polyuronic acid component is hydrophilic and theglyceryl poly(oxypropylene) triamine component is by design hydrophobic,finding a compatible solvent medium is potentially problematic. Theinventor of the present invention has found that slow addition of anaqueous solution of the polyuronic acid to an aqueous methanol solutioncontaining a large excess of the glyceryl poly(oxypropylene) triamineresults in the formation of a homogeneous solution.

For the purpose of achieving a homogeneous reaction is solution, suchthat two or more polyuronic acids can be covalently attached to a singleglyceryl poly(oxypropylene) triamine, the inventor of the presentinvention has found that strongly polar non-aqueous solvents areefficacious. Useful solvents in this class include dimethyl sulfoxide(DMSO), sulfolane, 1,3-dimethyl-2-imidazolidinone (DMI), andN-methyl-2-pyrrolidione (NMP). To facilitate the dissolution of thepolyuronic acids in these strongly polar solvents, the addition of arelatively small amount of trifluoroacetic acid, a non-aqueous strongacid, has been found to be useful. Similarly, to facilitate thedissolution of the glyceryl poly(oxypropylene) triamine, the addition ofa low-molecular-weight-alcohol cosolvent has been found to be useful. Ina preferred method, separate solutions are prepared containing theappropriate stoichiometric quantities of the polyuronic acid and theglyceryl poly(oxypropylene) triamine starting materials. The solutionsare then combined and mixed thoroughly. After a sufficient time periodhas elapsed, such that complete or near complete glycosylamination hasbeen achieved, the reductive amination reaction is carried out.

The reductive amination step may be carried out using any method knownto one skilled in the art. This reaction preferably carried out inhomogeneous reactant solution as described above. Reductive amination isconveniently carried out homogeneously using borane complexes,borohydride or cyanoborohydride salts. Typically used borane complexesinclude borane-ammonia complex, borane-tert-butylamine complex,borane-N,N-diethylaniline complex, borane-N,N-diisopropylethylaminecomplex, borane-dimethylamine complex, borane-N-ethyl-N-isopropylanilinecomplex, borane-4-ethylmorpholine complex, borane-morpholine complex,borane-pyridine complex, borane-triethylamine complex, andborane-trimethylamine complex. Typically used borohydride salts includesodium borohydride, potassium borohydride, lithium borohydride,tetramethylammonium borohydride, and tetrabutylammonium borohydride.Typically used cyanoborohydride salts include sodium cyanoborohydride,potassium cyanoborohydride, lithium cyanoborohydride, andtetrabutylammonium cyanoborohydride.

Another convenient and selective method is heterogeneous catalytichydrogenation using metal catalysts. Typical metal catalysts include anyof the Group VIII metals, with nickel, palladium, platinum, andruthenium being preferred. The metal catalysts may be used in eithersupported or unsupported forms. Hydrogen pressures are greater than 100psi (6.895×10⁵ Pa), and more preferably greater than 700 psi (4.827×10⁶Pa). Reaction temperatures are in the range of 10° C. to 100° C., andmore preferably in the range 30° C. to 60° C. Less selective reagentsfor reductive amination which may be used include 1) zinc and hydrogenchloride gas, 2) iron pentacarbonyl and alcoholic potassium hydroxide,and 3) formic acid.

In the polyuronic acid derivative according to the first embodiment ofthe present invention, isolation of the product is easily accomplishedby evaporating the reaction solvent and then washing the reactionproduct with a solvent that will selectively dissolve the unreactedglyceryl poly(oxypropylene) triamine, but will not dissolve the product.The unreacted glyceryl poly(oxypropylene) triamine may be recovered andused again as a starting material. After washing, the glycerylpoly(oxypropylene) triamine-free product may be dissolved in water withor without the addition of a neutralizing base.

In the polyuronic acid derivative according to the second embodiment ofthe present invention, isolation of the product may be accomplished byany method known in the art. When the reductive amination is carried outusing soluble borane complexes or borohydride salts, a preferred firststep in isolating the product is exhaustive evaporation of the reactionsolvent under reduced pressure. Finally, the reaction product is washedwith a solvent, which will selectively dissolve incompletely reactedreducing agents and their reaction products, and then dried. When thereductive amination is carried out using heterogeneous catalytichydrogenation, the product is isolated similarly to that above afterfirst removing the insoluble hydrogenation catalysts by filtration.Alkaline solution as products is prepared by using suitable base(example is shown below).

Subsequent purification of the resulting aqueous solution byultrafiltration is preferred where purity of the product is a majorconsideration.

All of the reaction and isolation process steps may be carried out asbatch processes or continuous processes according to methods known tothose skilled in the art.

The polyuronic acid derivatives according to the present invention aresimilar to the derivatives claimed in U.S. Pat. No. 6,242,529, with themajor difference being that the derivatives of the present invention maybe prepared from a low-cost hydrophobic polymer, a glycerylpoly(oxypropylene) triamine. Furthermore, the derivatives of the presentinvention may be prepared simply using the low-cost hydrophobic polymerwithout modification in a one-step reductive amination reaction.

Pigment Dispersed Aqueous Ink Composition

The pigment dispersed aqueous ink composition according to the thirdembodiment of the present invention comprises a water as a principalsolvent, a pigment, and a polyuronic acid derivative according to thefirst or second embodiment of the present invention as described above.

The amount of pigment dispersion comprising polyuronic acid derivetivesin the ink composition is about 0.1% to 20% by weight and morepreferably 0.1 to 10% by weight.

The components of the ink composition except the polyuronic acid aboveare described below.

<Pigment>

The pigment in the ink composition according to the present inventioncomprises at least one selected from the group consisting organic orinorganic pigments. The term “pigment” as used herein means an insolublecolorant.

The pigment particles are sufficiently small to permit free flow of thepigment-dispersed ink through the ink-jet printing device, especiallythrough the ejecting nozzles, which typically have a diameter, rangingfrom 10 to 50 microns. The particle diameter of the pigment ispreferably 10 microns or less and more preferably 0.1 microns or less.

The selected pigment may be used in dry or wet form. Usually pigmentsare manufactured in aqueous media and the resulting pigment is obtainedas a water wet presscake. In this presscake form, the pigment is notagglomerated to the extent that it is in a dry form. For preparingpigment dispersions, pigments in wet presscake form do not require asmuch deflocculation as do dry pigments.

Pigments of the present invention may include the following: SymulerFast Yellow GF (Dainippon Ink; C.I. Pigment Yellow 12), Symuler FastYellow GRF (Dainippon Ink; C.I. Pigment Yellow 13), Symuler Fast Yellow5GF (Dainippon Ink; C.I. Pigment Yellow 14), Irgalite Yellow CG(Ciba-Geigy; C.I. Pigment Yellow 16), Symuler Fast Yellow HGF (DainipponInk; C.I. Pigment Yellow 17), Symuler Fast Yellow 4117 (Dainippon Ink;C.I. Pigment Yellow 73), Symuler Fast Yellow 4191N (Dainippon Ink; C.I.Pigment Yellow 74), Symuler Fast Yellow 4181 (Dainippon Ink; C.I.Pigment Yellow 83), Chromophthal Yellow 3G (Ciba-Geigy; C.I. PigmentYellow 93), Chromophthal Yellow GR (Ciba-Geigy; C.I. Pigment Yellow 95),Symuler Fast Yellow 4186 (Dainippon Ink; C.I. Pigment Yellow 97), HansaBrilliant Yellow 10GX (Hoechst Celanese; C.I. Pigment Yellow 98),Permanent Yellow G3R-01 (Hoechst Celanese; C.I. Pigment Yellow 114),Chromophthal Yellow 8G (Ciba-Geigy; C.I. Pigment Yellow 128), IrgazinYellow 5GT (Ciba-Geigy; C.I. Pigment Yellow 129), Hostaperm Yellow H4G(Hoechst Celanese; C.I. Pigment Yellow 151), Symuler Fast Yellow 4192(Dainippon Ink; C.I. Pigment Yellow 154), Hostaperm Orange GR (HoechstCelanese; C.I. Pigment Orange 43), Paliogen Orange (BASF; C.I. PigmentOrange 51), Symuler Brilliant Carmine (Dainippon Ink; C.I. Pigment Red57:1), Fastogen Super Magenta (Dainippon Ink; C.I. Pigment Red 122),Paliogen Red L3870 (BASF; C.I. Pigment Red 123), Hostaperm Scarlet GO(Hoechst Celanese; C.I. Pigment Red 168), Permanent Rubine F6B (HoechstCelanese; C.I. Pigment Red 184), Monastral Magenta (Ciba-Geigy; C.I.Pigment Red 202), Monastral Scarlet (Ciba-Geigy; C.I. Pigment Red 207),Fastogen Blue GP-100 (Dainippon Ink; C.I. Pigment Blue 15:2), FastogenBlue GNPR (Dainippon Ink; C.I. Pigment Blue 15:3), Fastogen Blue GNPS(Dainippon Ink; C.I. Pigment Blue 15:4), Micracet Blue R (Ciba-Geigy;C.I. Pigment Blue 60), Fastogen Green S (Dainippon Ink; C.I. PigmentGreen 7), Fastogen Green 2YK (Dainippon Ink; C.I. Pigment Green 36),Fastogen Super Red (Dainippon Ink; C.I. Pigment Violet 19), FastogenSuper Violet (Dainippon Ink; C.I. Pigment Violet 23), Monastral MaroonRT-229-D (Ciba-Geigy; C.I. Pigment Violet 42), Raven 1170 (ColumbianChemicals; C.I. Pigment Black 7), Special Black 4A (Degussa; C.I.Pigment Black 7), S160 (Degussa; C.I. Pigment Black 7), S170 (Degussa;C.I. Pigment Black 7), FW 18 (Degussa; C.I. Pigment Black 7), and FW 18(Degussa; C.I. Pigment Black 7).

The amount of pigment in the ink composition of the present invention isabout 0.1% to 30% by weight and more preferably 0.1 to 20% by weight.

<Water>

Water is the principal solvent for the pigment dispersed aqueous inkcompositions of the present invention. Additional components, which maybe included in the ink compositions, are given below. The amount of theaqueous carrier medium in the ink composition of the present inventionis 70 to 99.8% by weight.

<Base>

To solubilize the polyuronic acid segments of the pigment dispersion inthe aqueous medium, it may be necessary to neutralize some or all of thecarboxylic acid functions. Bases, which are suitable for this purpose,include organic bases, alkanolamines, alkali metal hydroxides, andmixtures thereof. Examples of suitable bases include the following:methylamine, dimethylamine, trimethylamine, morpholine,N-methylmorpholine, monoethanolamine, diethanolamine, triethanolamine,N-methyl-monoethanolamine, N,N-dimethyl-monoethanolamine,N-methyl-diethanolamine, tri-isopropanolamine, tetramethylammoniumhydroxide, ammonia, lithium hydroxide, sodium hydroxide, potassiumhydroxide, rubidium hydroxide, and cesium hydroxide.

<Water-Soluble Cosolvents>

In addition to the above-described components, the inks may contain,optionally, one or more water-soluble organic solvents. Water-solubleorganic solvents are well known in the art and include: (1) alcoholssuch as isopropyl alcohol, butyl alcohols, etc. (2) ketones such asacetone, methyl ethyl ketone, etc. (3) ethers such as tetrahydrofuran,dioxane, etc. (4) esters such as ethyl acetate, propylene carbonate,etc. (5) polyhydric alcohols such as ethylene glycol, propylene glycol,butylene glycol, diethylene glycol, triethylene glycol, polyethyleneglycol, polypropylene glycol, 1,5-pentanediol, 1,2-pentanediol,1,2-hexanediol, 1,2,6-hexanetriol, 1,2-heptanediol, thiodiglycol,glycerol, etc. (6) lower alkyl ethers of polyhydric alcohols such asethylene glycol monomethyl ether, ethylene glycol monoethyl ether,ethylene glycol mono-n-propyl ether, ethylene glycol mono-isopropylether, ethylene glycol mono-n-butyl ether, ethylene glycolmono-sec-butyl ether, ethylene glycol mono-isobutyl ether, ethyleneglycol mono-tert-butyl ether, ethylene glycol mono-n-amyl ether,ethylene glycol mono-n-hexyl ether, propylene glycol monomethyl ether,propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether,propylene glycol mono-isopropyl ether, propylene glycol mono-n-butylether, propylene glycol mono-sec-butyl ether, propylene glycolmono-isobutyl ether, propylene glycol mono-tert-butyl ether, diethyleneglycol monomethyl ether, diethylene glycol monoethyl ether, diethyleneglycol mono-n-propyl ether, diethylene glycol mono-isopropyl ether,diethylene glycol mono-n-butyl ether, dipropylene glycol monomethylether, dipropylene glycol monoethyl ether, dipropylene glycolmono-n-propyl ether and dipropylene glycol mono-n-butyl ether, etc. (7)nitrogen containing compounds such as urea, pyrrolidone,N-methyl-2-pyrrolidone, etc. (8) sulfur containing compounds such asdimethylsulfoxide, tetramethylene sulfoxide, etc. No particularlimitation is imposed on the total amount of cosolvent to be used in theink. Preferably it is present in a range of 0.5 to 40 wt. %.

<Other Components>

In addition to the above-described components, the inks may contain,optionally, one or more penetrability-imparting surfactants selectedfrom the group consisting of anionic or non-ionic surfactants. Examplesof anionic surfactants include fatty acid salts, higher alcohol sulfuricester salts, alkylbenzene sulfonates, and higher alcohol phosphoricester salts. Examples of nonionic surfactants include ethylene oxideadducts of acetylenic diols, ethylene oxide adducts of higher alcohols,ethylene oxide adducts of alkylphenols, aliphatic ethylene oxideadducts, ethylene oxide adducts of higher alcohol fatty acid esters,ethylene oxide adducts of higher alkyl amines, ethylene oxide adducts offatty acid amides, ethylene oxide adducts of polypropylene glycol, fattyacid esters of polyhydric alcohols, alkanolamine fatty acid amides andethylene oxide-propylene oxide copolymers. Preferably used are theacetylenic diols or ethylene oxide adducts of acetylenic diols, whichare available from Air Products and Chemicals, Inc., Allentown, Pa.,18195, USA. Examples include Surfynol 104 (tetramethyl decynediol),Surfynol 465 (ethoxylated tetramethyl decynediol), Surfynol CT-136(acetylenic diol and anionic surfactant blend), Surfynol GA (acetylenicdiol blend) and Surfynol TG (acetylenic diol blend in ethylene glycol).Also preferably used are the ethoxylated and/or propoxylated siliconesurfactants, which are available from BYK Chemie GmbH, Germany. Noparticular limitation is imposed on the amount ofpenetrability-imparting surfactant to be used in the ink. Preferably itis present in a range of 0.01 to 5 wt. %. In addition to the abovepenetrability-imparting surfactants, the inks may contain additives suchas is pH buffers, biocides, viscosity modifiers, ultraviolet rayabsorbers, corrosion inhibitors and antioxidants. The amounts of allcomponents of the ink are selected such that the viscosity of the ink isless than 10 cps at 20° C.

Pigment Self-Dispersed Aqueous Ink Composition

The Pigment dispersed aqueous ink composition according to the presentinvention comprises water as a principal solvent, a self-dispersedpigment, and a polyuronic acid derivative according to the first orsecond embodiment of the present invention as described above.

The amount of polyuronic acid derivetives in the ink composition isabout 0.1% to 20% by weight and more preferably 0.1 to 10% by weight.

The components of the ink composition except the polyuronic acid aboveare described below.

<Self-Dispersed Pigment>

The self-dispersed pigment of the present invention comprises at leastone selected from the group consisting of self-dispersed organic orself-dispersed inorganic pigments, wherein the vehicle for theself-dispersed pigment is water. Although generally the term “pigment”is used to mean an insoluble colorant, the smaller particle sizefractions of self-dispersed pigments can be difficult to distinguishfrom a soluble colorant, such as a dye. Specifically, a non-negligiblefraction of a self-dispersed pigment can be resistant to completeseparation form the aqueous vehicle when the self-dispersed pigmentdispersion is subjected to large centrifugal forces such as thosegenerated in an ultracentrifuge. Nevertheless, for the purpose of ageneral definition, the term “pigment” as used herein refers to acolorant that is substantially an insoluble colorant, whereinsubstantially means greater than 95% by weight.

The term “self-dispersed,” when used to modify pigments is definedherein to mean a pigment which does not require dispersing agents, suchas polymeric dispersants or surfactants, to produce stable dispersionsof the pigment in the aqueous vehicle. The stability of such dispersionsis indicated by the constancy of their physicalcharacteristics—viscosity, surface tension, pH, and particle size—withrespect to time under actual conditions or under accelerated agingconditions. Because typical pigments have densities greater than water,it is inevitable that some settling will occur over time. High settlingrates are indicative of poor stability. For dispersions with highsettling rates, changes in physical characteristics concomitant withsettling will be readily measurable. Suitably low settling rates—forexample, less than 10% per year—indicates a high degree of stability. Adefining characteristic of a self-dispersed pigment is that the aqueousdispersion containing the self-dispersed pigment will have a surfacetension very close to that of water, 72 dynes/cm at 25° C. Polymericdispersants and surfactants tend to lower the surface tension of theunadulterated pigment dispersion to values less than 60 dynes/cm at 25°C.

The pigment upon which the self-dispersed pigment is based may beselected from the following group of pigments listed below.

For black pigments, carbon blacks produced by any known processes, suchas contact, furnace, gas, and thermal processes, may be used. Examplesinclude Raven 1170 (Columbian Chemicals; C.I. Pigment Black 7), SpecialBlack 4A (Degussa; C.I. Pigment Black 7), S160 (Degussa; C.I. PigmentBlack 7), 5170 (Degussa; C.I. Pigment Black 7), FW 18 (Degussa; C.I.Pigment Black 7), FW 200 (Degussa; C.I. Pigment Black 7), Raven 5000(Columbian Chemicals; C.I. Pigment Black 7), Raven 3500 (ColumbianChemicals; C.I. Pigment Black 7), CD 2038 (Columbian Chemicals; C.I.Pigment Black 7), CD 7035 (Columbian Chemicals; C.I. Pigment Black 7),CD 6026 (Columbian Chemicals; C.I. Pigment Black 7), CD 7004 (ColumbianChemicals; C.I. Pigment Black 7), MA 100 (Mitsubishi Chemical; C.I.Pigment Black 7), #45 (Mitsubishi Chemical; C.I. Pigment Black 7),Vulcan XC72R (Cabot; C.I. Pigment Black 7), Monarch 1000 (Cabot; C.I.Pigment Black 7), and Monarch 880 (Cabot; C.I. Pigment Black 7).

For non-black color pigments, any organic color pigment may be usedwithout any particular limitation. Examples of organic color pigments,usable as pigments upon which the self-dispersed pigments may be based,include azo, phthalocyanine, quinacridone, isoindolinone, dioxazine,benzimidazolone, anthraquinone, indanthrone, and perylene pigments.Pigments of the present invention may include the following: SymulerFast Yellow GF (Dainippon Ink; C.I. Pigment Yellow 12), Symuler FastYellow GRF (Dainippon Ink; C.I. Pigment Yellow 13), Symuler Fast Yellow5GF (Dainippon Ink; C.I. Pigment Yellow 14), Irgalite Yellow CG(Ciba-Geigy; C.I. Pigment Yellow 16), Symuler Fast Yellow HGF (DainipponInk; C.I. Pigment Yellow 17), Symuler Fast Yellow 4117 (Dainippon Ink;C.I. Pigment Yellow 73), Symuler Fast Yellow 4191N (Dainippon Ink; C.I.Pigment Yellow 74), Symuler Fast Yellow 4181 (Dainippon Ink; C.I.Pigment Yellow 83), Chromophthal Yellow 3G (Ciba-Geigy; C.I. PigmentYellow 93), Chromophthal Yellow GR (Ciba-Geigy; C.I. Pigment Yellow 95),Symuler Fast Yellow 4186 (Dainippon Ink; C.I. Pigment Yellow 97), HansaBrilliant Yellow 10GX (Hoechst Celanese; C.I. Pigment Yellow 98),Permanent Yellow G3R-01 (Hoechst Celanese; C.I. Pigment Yellow 114),Chromophthal Yellow 8G (Ciba-Geigy; C.I. Pigment Yellow 128), IrgazinYellow 5GT (Ciba-Geigy; C.I. Pigment Yellow 129), Hostaperm Yellow H4G(Hoechst Celanese; C.I. Pigment Yellow 151), Symuler Fast Yellow 4192(Dainippon Ink; C.I. Pigment Yellow 154), Toner Yellow HG (Clariant;C.I. Pigment Yellow 180), Hostaperm Orange GR (Hoechst Celanese; C.I.Pigment Orange 43), Paliogen Orange (BASF; C.I. Pigment Orange 51),Symuler Brilliant Carmine (Dainippon Ink; C.I. Pigment Red 57:1),Fastogen Super Magenta (Dainippon Ink; C.I. Pigment Red 122), TonerMagenta EO (Clariant; C.I. Pigment Red 122), Paliogen Red L3870 (BASF;C.I. Pigment Red 123), Hostaperm Scarlet GO (Hoechst Celanese; C.I.Pigment Red 168), Permanent Rubine F6B (Hoechst Celanese; C.I. PigmentRed 184), Monastral Magenta (Ciba-Geigy; C.I. Pigment Red 202),Monastral Scarlet (Ciba-Geigy; C.I. Pigment Red 207), Fastogen BlueGP-100 (Dainippon Ink; C.I. Pigment Blue 15:2), Fastogen Blue GNPR(Dainippon Ink; C.I. Pigment Blue 15:3), Toner Cyan B (Clariant; C.I.Pigment Blue 15:3), Fastogen Blue GNPS (Dainippon Ink; C.I. Pigment Blue15:4), Micracet Blue R (Ciba-Geigy; C.I. Pigment Blue 60), FastogenGreen S (Dainippon Ink; C.I. Pigment Green 7), Fastogen Green 2YK(Dainippon Ink; C.I. Pigment Green 36), Fastogen Super Red (DainipponInk; C.I. Pigment Violet 19), Fastogen Super Violet (Dainippon Ink; C.I.Pigment Violet 23), and Monastral Maroon RT-229-D (Ciba-Geigy; C.I.Pigment Violet 42).

The self-dispersed pigment of the present invention may be prepared byany method known in the art such that charged functionalities aredeliberately introduced onto the surface of the pigment particles insufficient numbers. Without intending to be limiting in regard to thepresent invention, methods for introducing charged functionalities onpigment surfaces include the following: oxidation by hypochlorite salts,oxidation by permanganate salts, oxidation by chlorate salts, oxidationby persulfate salts, oxidation by nitric acid, oxidation by ozone,coupling reactions with aryl diazonium salts that contain chargedfunctional groups, and sulfonation by sulfonating reagents. Commerciallyavailable black self-dispersed pigment dispersions are available fromCabot Corporation in two different product versions: CAB-O-JET 200 (asulfonated carbon black) and CAB-O-JET 300 (a carboxylated carbonblack). Another commercially available black self-dispersed pigmentdispersion is Bonjet Black CW-1, which is produced by Orient Chemical.

According to a preferred embodiment of the present invention, theself-dispersed pigment has an average particle size within the range 50to 200 nanometers. The amount of self-dispersed pigment in the inkcomposition of the present invention is about 0.1% to 30% by weight andmore preferably 0.1 to 20% by weight.

<Water, Base, Water-soluble Cosolvents, and Other Components>

With regard to water, base, water-soluble cosolvents, and othercomponents, the same components as described for the ink compositionaccording to the third embodiment of the present invention can be used.

<Ink Preparation>

The ink composition according to the third embodiment of the presentinvention may be prepared in one step by dispersing and mixing the abovedescribed components using an acceptable method. Alternatively, the inkcomposition may be prepared in two steps by 1) dispersing and mixingsome of the above described components and then 2) adding the remainingcomponents to the dispersion and mixing. The dispersing step may beaccomplished using a ball mill, a sand mill, an atrittor, a mini-mill, aroll mill, an agitator mill, a Henschel mixer, a colloid mill, anultrasonic homogenizer, a jet mill, or an angmill to obtain ahomogeneous dispersion.

It may be desirable to prepare first the pigmented ink in a concentratedform and then subsequently dilute the concentrated dispersion to aconcentration appropriate for use in the ink jet printer. Also, it isgenerally desirable to filter the pigment dispersed aqueous inkcomposition, preferably using a metal mesh filter or a membrane filter.Filtration may be accomplished by applying pressure to the inkcomposition being filtered or by reducing the pressure on the receivingend of the filtration device. Centrifugal separation may also be used toremove large particles that may cause obstruction of the nozzles on theprint head of the ink jet printer.

The ink composition according to the forth embodiment of the presentinvention may be prepared simply by mixing the above-describedcomponents using any acceptable method. In a preferred embodiment, aftercombining the components, the ink composition is heated with stirring ata temperature greater than 50° C. for a brief period of time such thatan ink with an unchanging viscosity is obtained. In another preferredembodiment, after combining the components, the ink composition issubjected to ultrasonication in an ultrasonication bath for a briefperiod of time such that an ink with an unchanging viscosity isobtained. After completing the above-described stabilizing treatments ora similar treatment, it is desirable to remove any large particles fromthe ink by filtration. This is preferably carried out using metal meshfilters or membrane filters. Filtration may be accomplished by applyingpressure to the ink being filtered or by reducing the pressure on thereceiving end of the filtration device. Prior to filtration, centrifugalseparation may be used to remove excessively large particles.

Without intending to be bound by theory, it is believed that the inkcomposition described herein gives reliable printing performance andyields printed images that have excellent print quality as a result of afavorable interaction between the polyuronic acid derivative, in which aglyceryl poly(oxypropylene) triamine is reductively aminated to thereducing terminus of the polyuronic acid, and the self-dispersedpigment. That an interaction between these two main components occurs isevidenced by a small viscosity rise that occurs when the freshlyprepared ink mixture is heated or treated ultrasonically as describedabove as a preferred embodiment for ink preparation. Oligo-oxypropylenepolymers are known to have decreased aqueous solubility as thetemperature of the aqueous medium is increased. The glycerylpoly(oxypropylene) triamine segment of the polyuronic acid derivative,in which polyuronic acid is attached by reductively amination, throughreducing terminus of the polyuronic acid, to glyceryl poly(oxypropylene)triamine, is expected to exhibit similar behavior. By heating themixture (bulk increased temperature) or treating the mixtureultrasonically (localized increased temperature), the glycerylpoly(oxypropylene) triamine segment is made less compatible with theaqueous medium and more compatible with any hydrophobic species, whichmay be present. In the ink composition of the present invention, theself-dispersed pigment component is such a hydrophobic species. Althoughthe surfaces of self-dispersed pigments are more hydrophilic thancomparable unmodified pigments, the degree of surface functionalizationis still relatively small and the bulk of the pigment surface isconsiderably hydrophobic. Thus, it is not unreasonable that aninteraction occurs between these two main ink components when the inkmixture is heated in the bulk or locally. The relatively high molecularweight of the poly(oxypropylene) triamine segment hinders dissociationof the poly(oxypropylene) triamine segment after interaction andsubsequent adsorption occurs. Thus, on the time scale of ink storageand/or ink usage (several years), the initial small viscosity rise isnot reversed and an unchanging ink viscosity is obtained.

Without intending to be bound by theory, it is believed that the inkcomposition according to the present invention gives reliable printingperformance because the self-dispersed pigment retains the usefulcharacteristics of an unmodified self-dispersed pigment even afteradsorption onto the pigment surface by the polyuronic acid derivativeaccording to the present invention. As noted above, the use ofself-dispersed pigments is one of the most general approaches forobtaining reliable printing performance using aqueous pigment-basedinks. The excellent water solubility of the polyuronic acid segment issuch that, not only are the useful characteristics of a self-dispersedpigment retained, the stability of theself-dispersed-pigment/polyuronic-acid-derivative combination isexpected to be enhanced.

Without intending to be bound by theory, it is believed that the inkcomposition according to the present invention yields excellent printquality on plain paper because the self-dispersed pigment retains theuseful characteristics of an unmodified self-dispersed pigment as notedabove. The inclusion of the polyuronic acid derivative, in whichpolyuronic acid is attached by reductively amination, through reducingterminus of the polyuronic acid, results in only a small viscosity risefor the ink formulation as noted above. As a consequence of this smallviscosity rise, inks of the present invention may be formulated with therelatively high pigment contents that are typical of inks containingunmodified self-dispersed pigments. High pigment contents translate intohigh optical densities on plain paper, a defining characteristic forexcellent plain-paper print quality.

Furthermore, without intending to be bound by theory, it is believedthat the ink composition according to the present invention yieldsexcellent print quality on coated specialty media that exhibitlustrousness as a result of a favorable adsorption onto the surface ofthe self-dispersed pigment by the polyuronic acid derivative, in whichpolyuronic acid is attached by reductively amination, through reducingterminus of the polyuronic acid, to glyceryl poly(oxypropylene)triamine. In contrast to the water-based resins, emulsion additives,water-soluble emulsions, soluble and/or dispersed polymers, and acrylicresins given as examples of the prior art, the polyuronic acidderivative, in which polyuronic acid is attached by reductivelyamination, through reducing terminus of the polyuronic acid, to glycerylpoly(oxypropylene) triamine, may be forcibly adsorbed onto the surfaceof the self-dispersed pigments as described above. The adsorbedpolyuronic acid, in which polyuronic acid is attached by reductivelyamination, through reducing terminus of the polyuronic acid, to glycerylpoly(oxypropylene) triamine, is able then to function as a glaze forimproving the lustrousness of the printed images on coated specialtymedia. Because the form of theself-dispersed-pigment/polyuronic-acid-derivative combination is similarto that of non-self-dispersed pigment dispersions, lustrousness andadhesion comparable to that of non-self-dispersed pigment dispersionsare obtained.

EXAMPLES

The present invention will be further described in more detail withreference to the following examples, though it is not limited to theseexamples only.

1. Preparation of Pigment Dispersion Comprising Polyuronic AcidDerivative According to the First Embodiment

(1) Preparation of Polyguluronic Acid

A four neck 1 L round bottom flask equipped with a thermometer, anoverhead mechanical stirrer, and a condenser was placed snugly into avariable temperature controlled heating mantle. 600 g of 81% formic acid(prepared from deionized water and 88% reagent grade formic acid fromKanto Chemicals, Japan) was transferred to the flask. Next, the formicacid was warmed to 90° C. with gentle stirring. While stirringvigorously, 45 g of apple pectin (Classic AM 201, Herbstreith & Fox,Switzerland) was added gradually to the hot formic acid using a powderfunnel. The fourth neck of the flask was sealed with a glass stopperafter quickly purging the system with a brisk flow of nitrogen. Afterthe purge, a nitrogen inlet adapter connected to an oil bubbler wasfitted to the top of the condenser and a slow controlled flow ofnitrogen through the oil bubbler was started. The pectin completelydissolved after stirring vigorously for 60 minutes. Next, the solutionwas heated to reflux while stirring the solution moderately. The heatingat reflux and stirring were continued for 5 hours and then the solutionwas allowed to cool to about 40° C. The warm solution was filteredthrough a #1 Whatman filter into a 1 L Erlenmeyer flask in order toremove a small amount of brown insoluble impurities. The collectedfiltrate was transferred to a 1 L pear-shaped flask. Using a rotaryevaporator with a circulating-type aspirator and a water bath setting of60° C., the solvent was evaporated until a viscous light brown oilremained in the flask. 700 mL of ethanol was added to the flaskresulting in the immediate precipitation of an off-white crystallinesolid. The solid was collected by filtration through a fine porosity(pore size: 16–40 microns) fritted glass filter using an aspirator toreduce the pressure in the collecting flask. The solid was washed twicewith approximately 400 mL portions of ethanol and then set aside to airdry. Finally, the solid was dried under vacuum to a constant weight. Theyield of product was 14.5 g. The degree of polymerization of the productwas determined to be 21.2 using the method of P. A. Shaffer and M.Somogyi (J. Biol. Chem., 100, 695–713 (1933)). The product also wascharacterized by ¹H NMR in dimethyl-d₆ sulfoxide ((CD₃)₂SO) andtrifluoroacetic acid-d₁ (CF₃CO₂D) and by ¹³C NMR in D₂O. Both spectraare consistent with a mixture of high purity polygalacturonic acids.

(2) Preparation of Polyguluronic Acid

150 g of alginic acid (Ultra Low Viscosity Alginic Acid; Kibun FoodChemiphar; Tokyo, Japan) was slurried in 450 mL of deionized water in a1000 mL beaker. To this slurry was added 28.0 g of lithium hydroxidemonohydrate, while stirring the slurry with an overhead mechanicalstirrer. The alginic acid dissolved to yield a solution with a pH valueof approximately 4.15. Deionized water was added to give a totalsolution volume of 600 mL. Next, 100 g of 31 wt. % hydrogen peroxidesolution and 2 mL of n-nonyl alcohol, as a defoaming agent, were addedwith stirring. A 40 mL solution containing 0.65 g of ferrous sulfateheptahydrate was freshly prepared and added to the alginic-acid/hydrogenperoxide solution with stirring. The solution was stirred vigorously forfour hours during which time a substantial exotherm occurred and thensubsided. While the solution was still warm (about 40° C.), anadditional 20 g of 31 wt. % hydrogen peroxide solution was added withstirring. While stirring the solution vigorously for an additional twohours, a mild exotherm occurred. Next, the mixture was heated at 60° C.for 30 minutes and then filtered hot through a sheet of #1 Whatmanfilter paper. After cooling to room temperature, the filtrate solutionwas transferred to a 1 L pear-shaped flask. Using a rotary evaporatorand a water bath setting of 60° C., the solution was concentrated to avolume of about 250 mL. Next, the solution was transferred to a 1 Lbeaker along with water washings, which brought the total volume up to300 mL. While stirring the solution vigorously, 300 mL of glacial aceticacid was added slowly which resulted in the precipitation of a solid.The solid that precipitated was collected by vacuum filtration using afine porosity (pore size: 16–40 microns) fritted glass filter. The wetsolid was transferred to a 1 L beaker along with approximately 100 mL ofdeionized water. The solid and water were stirred vigorously such that ahomogeneous slurry was obtained. While continuing to stir the slurry,800 mL of 95% ethanol was added. After stirring for 1 hour, the solidwas collected by vacuum filtration using a fine porosity (pore size:16–40 microns) fritted glass filter. The solid was washed with severalportions of 95% ethanol and then set aside to air dry. Finally, thesolid was dried under vacuum to a constant weight. The yield of productwas 18.5 g. The degree of polymerization was determined to be 13.2 usingthe method of R A. Shaffer and M. Somogyi as described above. Theproduct also was characterized by ¹H NMR in dimethyl-d₆ sulfoxide((CD₃)₂SO) and trifluoroacetic acid-d₁ (CF₃CO₂D). The spectrum wasconsistent with a mixture of pure polyguluronic acid and a mixedpolyuronic acid, which was mostly guluronic acid, but also contained asmall amount of mannuronic acid impurity. The guluronic acid content ofthe mixed product was greater than 85%.

(3) Preparation of Polyuronic Acid Derivative A1: glycerylpoly(oxypropylene) triamine Reductively Aminated to PolygalacturonicAcid

40 g of polygalacturonic acid, prepared as described above, was slurriedin 200 mL of deionized water in a 200 mL beaker. While stirring with amagnetic stir bar, the mixture was heated to about 50° C. such the mostof the polygalacturonic acid dissolved. 200 g of glycerylpoly(oxypropylene) triamine (Jeffamine XJT-509, x+y+z, equal to about50, Huntsman Corporation, Performance Chemicals Division, Houston, Tex.,USA), a football-type magnetic stir bar, 1200 g of methanol, and 200 gof deionized water were added to a 2 L beaker. Upon stirring thesolution using a magnetic stirrer, a homogeneous solution was obtained.While stirring the methanolic glyceryl poly(oxypropylene) triaminesolution, the warm aqueous slurry of polygalacturonic acid was addedquickly to the methanolic glyceryl poly(oxypropylene) triamine solution.While stirring the mixture continuously for 2 hours, a homogeneous brownsolution was obtained. The beaker was covered with a plastic wrap andset aside to stand for 60 hours. Next, roughly two-thirds of thepolygalacturonic-acid/glyceryl-poly(oxypropylene)-triamine solution wastransferred to a 1 L pear-shaped flask. Using a rotary evaporator and awater bath setting of 70° C., the solution was concentrated to a volumeof about 350 mL. After disconnecting, the pear-shaped flask from therotary evaporator, the remaining one-third of thepolygalacturonic-acid/glyceryl-poly(oxypropylene)-triamine solution wastransferred to the pear-shaped flask. Again, using the rotary evaporatorand a water bath setting of 70° C., the solution was concentrated untilno further volatile solvents were collected and a dark brown oilremained in the 1 L pear-shaped flask. The oil was washed with three 500mL portions of 75% methanol/25% ethanol with the washings beingdiscarded. As a consequence of the washings, the oil partiallysolidified. The tacky brown solid was dissolved in a mixed solutioncontaining 950 mL of methanol and 300 mL of 98% formic acid and thentransferred to a 2 L beaker. While stirring the solution using amagnetic stirrer and a football-type magnetic stir bar, 20 g ofborane-dimethyl amine complex was added. The complex dissolvedimmediately and the combined solution was stirred for an additional 36hours. During this time the color of the solution lightenedconsiderably. Next, using the rotary evaporator and a water bath settingof 70° C., as described above, the solution was concentrated to asolution volume of 400 mL. Next, 600 mL of deionized water, 600 mL ofisopropanol, and 200 mL of 98% formic acid was added to the solution andthe combined solution was transferred to a 2 L flask. While stirring thesolution, the solution was purified by ultrafiltration using a MilliporeMinitan system configured with twelve polysulfone plates having amembrane pore size rating of 10,000 molecular weight. The purifiedliquid was re-circulated to the original container while theglyceryl-poly(oxypropylene)-triamine-containing liquid permeate, whichpassed through the membrane, was collected for disposal. Additionaldeionized water/isopropanol/formic-acid solution was added periodicallyto the 2 L flask to compensate for the liquid permeate being removed. Inthe course of the ultrafiltration, the solution was concentrated to avolume of about 500 mL. The combined volume of collected liquid permeatewas about 5 liters. The resulting purified solution was filtered underpressure through a 5-micron membrane filter to remove a small amount ofsolid impurity. The volatile solvents were evaporated from the filtrateusing the rotary evaporator and a water bath setting of 70° C., asdescribed above. A light brown oil remained that was further dried to aconstant weight using an oil-type vacuum pump. The yield of product was57.5 g. A 300 mL flask was loaded with 30.0 g of the dried solid and 150g of deionized water. The mixture was stirred vigorously with warming toapproximately 40° C. and solid lithium hydroxide was added graduallyuntil most of the solid dissolved and the pH of the mixture wasapproximately 7.5. While monitoring the pH of the mixture, an aqueoussolution of lithium hydroxide monohydrate (5 wt. %) was added dropwisewith stirring until the pH reached a constant value of 8.5. Additionalwater was added such that a total solution weight of 200 g was obtained.For the final step, the resulting solution was filtered through a5-micron membrane filter.

The polyuronic acid derivative A1 thus obtained was used as the pigmentdispersant A1.

(4) Preparation of Polyuronic Acid Derivative B1: glycerylpoly(oxypropylene) triamine Reductively Aminated to Polyguluronic Acid

40 g of polyguluronic acid, prepared as described above, was slurried in200 mL of deionized water in a 200 mL beaker. 200 g of glycerylpoly(oxypropylene) triamine (Jeffamine XJT-509, x+y+z, equal to about50, Huntsman Corporation, Performance Chemicals Division, Houston, Tex.,USA), a football-type magnetic stir bar, 1000 g of methanol, and 200 gof deionized water were added to a 2 L beaker. Upon stirring thesolution using a magnetic stirrer, a homogeneous solution was obtained.While stirring the methanolic glyceryl poly(oxypropylene) triaminesolution, the aqueous slurry of polyguluronic acid was added quickly tothe methanolic glyceryl poly(oxypropylene) triamine solution. Whilestirring the mixture continuously for 2 hours, a homogeneous brownsolution was obtained. The beaker was covered with a plastic wrap andset aside to stand for 60 hours. Next, roughly two-thirds of thepolyguluronic-acid/glyceryl-poly(oxypropylene)-triamine solution wastransferred to a 1 L pear-shaped flask. Using a rotary evaporator and awater bath setting of 70° C., the solution was concentrated to a volumeof about 300 mL. After disconnecting, the pear-shaped flask from therotary evaporator, the remaining one-third of thepolyguluronic-acid/glyceryl-poly(oxypropylene)-triamine solution wastransferred to the pear-shaped flask. Again, using the rotary evaporatorand a water bath setting of 70° C., the solution was concentrated untilno further volatile solvents were collected and a dark brown oilremained in the 1 L pear-shaped flask. The oil was washed with three 500mL portions of 75% methanol/25% ethanol with the washings beingdiscarded. As a consequence of the washings, the oil partiallysolidified. The tacky brown solid was dissolved in a mixed solutioncontaining 950 mL of methanol and 300 mL of 98% formic acid and thentransferred to a 2 L beaker. While stirring the solution using amagnetic stirrer and a football-type magnetic stir bar, 20 g ofborane-dimethyl amine complex was added. The complex dissolvedimmediately and the combined solution was stirred for an additional 36hours. During this time the color of the solution lightenedconsiderably. Next, using the rotary evaporator and a water bath settingof 70° C., as described above, the solution was concentrated until nofurther volatile solvents were collected and a dark brown oil remainedin the 1 L pear-shaped flask. Next, 800 mL of deionized water, 600 mL ofisopropanol, and 200 mL of 98% formic acid was added to the solution andthe combined solution was transferred to a 2 L flask. While stirring thesolution, the solution was purified by ultrafiltration using a MilliporeMinitan system configured with twelve polysulfone plates having amembrane pore size rating of 10,000 molecular weight. The purifiedliquid was re-circulated to the original container while theglyceryl-poly(oxypropylene)-triamine-containing liquid permeate, whichpassed through the membrane, was collected for disposal. Additionaldeionized water/isopropanol/formic-acid solution was added periodicallyto the 2 L flask to compensate for the liquid permeate being removed. Inthe course of the ultrafiltration, the solution was concentrated to avolume of about 500 mL. The combined volume of collected liquid permeatewas about 5 liters. The resulting purified solution was filtered underpressure through a 5-micron membrane filter to remove a small amount ofsolid impurity. The volatile solvents were evaporated from the filtrateusing the rotary evaporator and a water bath setting of 70° C., asdescribed above. A light brown oil remained that was further dried to aconstant weight using an oil-type vacuum pump. The yield of product was52.8 g. A 300 mL flask was loaded with 30.0 g of the dried solid and 150g of deionized water. The mixture was stirred vigorously with warming toapproximately 40° C. and solid lithium hydroxide was added graduallyuntil most of the solid dissolved and the pH of the mixture wasapproximately 7.5. While monitoring the pH of the mixture, an aqueoussolution of lithium hydroxide monohydrate (5 wt. %) was added dropwisewith stirring until the pH reached a constant value of 8.8. Additionalwater was added such that a total solution weight of 200 g was obtained.For the final step, the resulting solution was filtered through a5-micron membrane filter.

The polyuronic acid derivative B1 thus obtained was used as the pigmentdispersant B1.

2. Preparation of Pigment Dispersant Comprising the Polyuronic AcidDerivative According to the Second Embodiment

(1) Preparation of Polygalacturonic Acid

A four neck 1 L round bottom flask equipped with a thermometer, anoverhead mechanical stirrer, and a condenser was placed snugly into avariable temperature controlled heating mantle. 600 g of 81% formic acid(prepared from deionized water and 88% reagent grade formic acid fromKanto Chemicals, Japan) was transferred to the flask. Next, the formicacid was warmed to 90° C. with gentle stirring. While stirringvigorously, 45 g of apple pectin (Classic AM 201, Herbstreith & Fox,Germany) was added gradually to the hot formic acid using a powderfunnel. The fourth neck of the flask was sealed with a glass stopperafter quickly purging the system with a brisk flow of nitrogen. Afterthe purge, a nitrogen inlet adapter connected to an oil bubbler wasfitted to the top of the condenser and a slow controlled flow ofnitrogen through the oil bubbler was started. The pectin completelydissolved after stirring vigorously for 30 minutes. Next, the solutionwas heated to reflux while stirring the solution moderately. The heatingat reflux and stirring were continued for 90 minutes and then thesolution was allowed to cool to about 40° C. The warm solution wasfiltered through a #1 Whatman filter into a 1 L Erlenmeyer flask inorder to remove a small amount of brown insoluble impurities. Thecollected filtrate was transferred to a 1 L pear-shaped flask. Using arotary evaporator with a circulating-type aspirator and a water bathsetting of 60° C., the solvent was evaporated until a viscous lightbrown oil remained in the flask. 700 mL of ethanol was added to theflask resulting in the immediate precipitation of an off-whitecrystalline solid. The solid was collected by filtration through a fineporosity (pore size: 16–40 microns) fritted glass filter using anaspirator to reduce the pressure in the collecting flask. The solid waswashed twice with approximately 400 mL portions of ethanol and then setaside to air dry. Finally, the solid was dried under vacuum to aconstant weight. The yield of product was 32.7 g. The product wascharacterized by ¹H NMR in dimethyl-d₆ sulfoxide ((CD₃)₂SO) andtrifluoroacetic acid-d₁ (CF₃CO₂D) and by ¹³C NMR in D₂O. Both spectraare consistent with a mixture of high purity polygalacturonic acids. Asa rough measure of the average molecular weight of the product, gelpermeation chromatographic analysis was carried out with respect tomalto-oligomer and dextran standards. A Hitachi Model L-6000 pump wasused in combination with a Gasukuro Kogyo Model 556 constant temperatureoven, a Shodex Model RI SE-52 refractive index detector, and a HitachiModel D2520 GPC integrator. The analysis was performed using a TSK-GELG3000PW_(XL) column (7.8 mm i.d.×30 cm) with a preceding TSK PW_(XL)Guard Column (6 mm i.d.×4 cm). The eluant was a phosphate buffer (pH 7)that was 0.06 molar in sodium dihydrogen phosphate dihydrate and 0.036molar in sodium hydroxide. The flow rate was 0.8 ml/minute and thecolumns were maintained at 25° C. Samples were prepared in the eluant atconcentrations of 1 wt. %; the injection volume was 40 microliters.Standard solutions of maltotriose, maltotetrose, maltopentose, dextran1080 g/mole, dextran 4440 g/mole, and dextran 9890 g/mole were used toconstruct a reference curve. With respect to the reference curve, theaverage molecular weight of the polygalacturonic acid sample wasapproximately 7300 g/mole.

(2) Preparation of Polyguluronic Acid

150 g of alginic acid (Ultra Low Viscosity Alginic Acid; Kibun FoodChemiphar; Tokyo, Japan) was slurried in 450 mL of deionized water in a1000 mL beaker. To this slurry was added 28.0 g of lithium hydroxidemonohydrate, while stirring the slurry with an overhead mechanicalstirrer. The alginic acid dissolved to yield a solution with a pH valueof approximately 4.15. Deionized water was added to give a totalsolution volume of 600 mL. Next, 100 g of 31 wt. % hydrogen peroxidesolution and 2 mL of n-nonyl alcohol, as a defoaming agent, were addedwith stirring. A 40 mL solution containing 0.65 g of ferrous sulfateheptahydrate was freshly prepared and added to the alginic-acid/hydrogenperoxide solution with stirring. The solution was stirred vigorously forfour hours during which time a substantial exotherm occurred and thensubsided. While the solution was still warm (about 40° C.), the solutionwas filtered hot through a sheet of #1 Whatman filter paper. Aftercooling to room temperature, the filtrate solution was transferred to a1 L pear-shaped flask. Using a rotary evaporator and a water bathsetting of 60° C., the solution was concentrated to a volume of about250 mL. Next, the solution was transferred to a 1 L beaker along withwater washings, which brought the total volume up to 300 mL. Whilestirring the solution vigorously, 300 mL of glacial acetic acid wasadded slowly which resulted in the precipitation of a solid. The solidthat precipitated was collected by vacuum filtration using a fineporosity (pore size: 16–40 microns) fritted glass filter. The wet solidwas transferred to a 1 L beaker along with approximately 100 mL ofdeionized water. The solid and water were stirred vigorously such that ahomogeneous slurry was obtained. While continuing to stir the slurry,800 mL of 95% ethanol was added. After stirring for 1 hour, the solidwas collected by vacuum filtration using a fine porosity (pore size:16–40 microns) fritted glass filter. The solid was washed with severalportions of 95% ethanol and then set aside to air dry. Finally, thesolid was dried under vacuum to a constant weight. The yield of productwas 18.5 g. The product was characterized by ¹H NMR in dimethyl-d₆sulfoxide ((CD₃)₂SO) and trifluoroacetic acid-d₁ (CF₃CO₂D). The spectrumwas consistent with a mixture of pure polyguluronic acid and a mixedpolyuronic acid, which was mostly guluronic acid, but also contained asmall amount of mannuronic acid impurity. The guluronic acid content ofthe mixed product was greater than 85%. As a rough measure of theaverage molecular weight of the product, gel permeation chromatographicanalysis was carried out with respect to malto-oligomer and dextranstandards, as described above. With respect to the reference curve, theaverage molecular weight of the polyguluronic acid sample wasapproximately 6200 g/mole.

(3) Preparation of Pigment Dispersant A Comprising the Polyuronic AcidDerivative A2: glyceryl poly(oxypropylene) triamine Reductively Aminatedto the Reducing Termini of Two or More Polygalacturonic Acids

60 g of the polygalacturonic acid, prepared as described above, and wasslurried in a solution of 6 g of trifluoroacetic acid in 450 mL of1,3-dimethyl-2-imidazolidinone contained in a 1 L beaker. While stirringwith a magnetic stir bar, the mixture was heated to about 50° C. suchthat nearly all of the polygalacturonic acid dissolved. While stirringwith a magnetic stir bar, 40 g of glyceryl poly(oxypropylene) triamine(JeffamineT-5000, x+y+z, equal to about 80, Huntsman Corporation,Performance Chemicals Division, Houston, Tex., USA) was dissolved in 200mL of 1,3-dimethyl-2-imidazolidinone contained in a 500 mL beaker. Whilestirring the polygalacturonic acid solution vigorously, the solution ofglyceryl poly(oxypropylene) triamine was added quickly to thepolygalacturonic acid solution. The resulting homogeneous light brownsolution was transferred to a 1 L wide-mouthed polyethylene samplebottle. The neck of the sample bottle was wrapped with Teflon tape andthe bottle was capped and sealed tightly. The sample bottle was storedin a 40° C. constant temperature oven for 48 hours. The sample bottlewas removed from the oven and set aside to cool to room temperature. Thecooled sample bottle was opened and 15 g of borane-dimethylamine complexwas added and the mixture swirled to bring about dissolution of theborane complex. The sample bottle was sealed as before and stored in thesame 40° C. constant temperature oven for 22 hours. During the 22-hourperiod, a significant amount of solid had precipitated from thesolution. The sample bottle was removed from the oven and set aside tocool to room temperature. The cooled sample bottle was opened andtrifluoroacetic acid was added in small portions followed by agitationof the mixture until a homogeneous solution was again achieved. Theadded amount of trifluoroacetic acid was approximately 10 g. The samplebottle was sealed as before and stored in the same 40° C. constanttemperature oven for 48 hours. The sample bottle was removed from theoven and set aside to cool to room temperature. The cooled sample bottlewas opened and the contents were poured into 4 L of vigorously stirredisopropanol contained in a 5 L beaker. Using a pH meter to monitor thepH of the mixture, 10 wt. % lithium hydroxide solution was addeddropwise to the well-stirred mixture until the pH value of the mixturewas greater than about 8. The stirred mixture was set aside to settlefor 15 hours. The light yellow supernatant, which had separated, wasremoved by decantation and discarded. Isopropanol was added to themixture to bring the total volume up to 4.5 L and the mixture wasstirred vigorously for 2 hours and then set aside to stand for 21 hours.This general process—decantation of the supernatant, addition ofisopropanol, stirring, and standing—was repeated three times. Afterstanding, the nearly colorless supernatant was removed and discarded asbefore. The remaining mixture was homogenized by treating the mixturecontained in the 5 L beaker in an ultrasonication bath for 30 minutes.The product solid was isolated by centrifuging the mixture in 50 mLtubes at 20,000 rpm for 8 minutes. The centrifuge tubes were placed in awell-ventilated draft hood for 24 hours. During this short drying periodthe solid separated from the centrifuge tube walls. The partially driedsolid was transferred to a sample bottle and dried under vacuum to aconstant weight. The yield of crude product was 88 g. The crude productwas dissolved in 800 mL of deionized water and filtered through a0.2-micron membrane filter. The filtrate was transferred to a 1 L flask.While stirring the solution, the solution was purified byultrafiltration using a Millipore Pellicon 2 Mini system configured witha single regenerated cellulose plate having a membrane pore size ratingof 10,000 Daltons (Part # P2C010C01). The purified solution wasrecirculated to the original container while the impurity containingpermeate solution was collected for disposal. Additional deionized waterwas added periodically to the 1 L flask to compensate for the permeatesolution being removed. In the course of the ultrafiltration, thesolution was concentrated to a final volume of about 400 mL. Thecombined volume of collected permeate solution was about 5 liters. Usinga pH meter to monitor the solution pH, 5 wt. % lithium hydroxidesolution was added dropwise to the solution while stirring until the pHvalue reached 8.9. The resulting solution was filtered under pressurethrough a 0.2-micron membrane filter to remove a small amount of solidimpurity. Two grams of the solution were accurately weighed and thenheated to dryness and constant weight in a 70° C. constant temperatureoven. The dried sample was accurately weighed and from the differencebetween the original weight and the dried weight, the concentration ofsolids in the solution was calculated. The polyuronic acid derivative A2having a concentration of solids in the solution of 14.6 wt. % wasobtained.

The polyuronic acid derivative A2 thus obtained was used as the pigmentdispersant A.

(4) Preparation of Pigment Dispersant B Comprising the Polyuronic AcidDerivative B2: glyceryl poly(oxypropylene) triamine Reductively Aminatedto the Reducing Termini of Two or More Polyguluronic Acids

56 g of the polyguluronic acid, prepared as described above, and wasslurried in a solution of 6 g of trifluoroacetic acid in 450 mL of1,3-dimethyl-2-imidazolidinone contained in a 1 L beaker. While stirringwith a magnetic stir bar, the mixture was heated to about 50° C. suchthat nearly all of the polyguluronic acid dissolved. While stirring witha magnetic stir bar, 44 g of glyceryl poly(oxypropylene) triamine(JeffamineT-5000, x+y+z, equal to about 80, Huntsman Corporation,Performance Chemicals Division, Houston, Tex., USA) was dissolved in 200mL of 1,3-dimethyl-2-imidazolidinone contained in a 500 mL beaker. Whilestirring the polyguluronic acid solution vigorously, the solution ofglyceryl poly(oxypropylene) triamine was added quickly to thepolyguluronic acid solution. The resulting homogeneous light brownsolution was treated from this point in the same way as that describedabove for the preparation of Pigment Dispersion A2. The yield of crudePigment Dispersion B product was 84.5 g. The calculated concentration ofPigment Dispersion B solids in the final solution of was 14.3 wt. %.

The polyuronic acid derivative B2 thus obtained was used as the pigmentdispersant B.

(5) Pigment Dispersant C1 (Comparative Example)

[45] Joncryl 62 (SC Johnson Polymer; acrylic resin solution; 34 wt. %solids) was used as is for preparing pigment dispersant.

(6) Pigment Dispersant D1 (Comparative Example)

The polymer dispersant used in this comparative example was a butylmethacrylate//methyl methacrylate/methacrylic acid block copolymer(BMA//MMA/MA) prepared according to the method described in U.S. Pat.No. 5,085,698. The block copolymer was neutralized with potassiumhydroxide and diluted such that a solution containing 25 wt. % solidswas obtained. This solution was filtered through a 5-micron membranefilter to prepare the pigment dispersant D1.

3. Preparation of Pigment Dispersion

30 g of the pigment, the pigment dispersant above, and a deionized waterwere mixed in the ratio which is shown in Table 1, and the mixture wasdispersed in an Eiger Motormill M250 VSE-EXJ (Eiger Japan, Tokyo,JAPAN). Glass beads (diameter: 1.0 mm), which had a total combinedvolume of 175 mL, were used as the milling media. Milling was carriedout at 4500 rpm for a period of 30 hours.

The yield of the pigment dispersion was about 200 g. The dispersioncombinations shown in Table 1 below were prepared. For all of thedispersions, the average particle size was between 100 and 120nanometers.

TABLE 1 Deionized Pigment Pigment Dispersant Water Dispersion PigmentSolution (weight) (weight) Black A1 Black FW 18 Pigment Dispersant 120 g(Degussa) A1 (100 g) Black B1 Black FW 18 Pigment Dispersant 120 g(Degussa) B1 (100 g) Cyan A1 Toner Cyan B Pigment Dispersant 100 g(Clariant) A1(120 g) Cyan B1 Toner Cyan B Pigment Dispersant 100 g(Clariant) B1 (120 g) Yellow A1 Toner Yellow HG Pigment Dispersant 100 g(Clariant) A1 (120 g) Yellow B1 Toner Yellow HG Pigment Dispersant 100 g(Clariant) B1 (120 g) Magenta A1 Toner Magenta EO Pigment Dispersant 100g (Clariant) A1 (120 g) Magenta B1 Toner Magenta EO Pigment Dispersant100 g (Clariant) B1 (120 g) Comp. Ex. Black FW 18 Pigment Dispersant 176g Black C (Degussa) C1 (44 g) Black D Black FW 18 Pigment Dispersant 160g (Comparative (Degussa) D1 (60 g) Example) Cyan D Toner Cyan B PigmentDispersant 148 g (Comparative (Clariant) D1 (72 g) Example) Black A2Black FW 18 Pigment Dispersant 117 g (Degussa) A2 (103 g) Black B2 BlackFW 18 Pigment Dispersant 115 g (Degussa) B2 (105 g) Cyan A2 Toner Cyan BPigment Dispersant 97 g (Clariant) A2 (123 g) Cyan B2 Toner Cyan BPigment Dispersant 94 g (Clariant) B2 (126 g) Yellow A2 Toner Yellow HGPigment Dispersant 97 g (Clariant) A2 (123 g) Yellow B2 Toner Yellow HGPigment Dispersant 94 g (Clariant) B2 (126 g) Magenta A2 Toner MagentaEO Pigment Dispersant 97 g (Clariant) A2 (123 g) Magenta B2 TonerMagenta EO Pigment Dispersant 94 g (Clariant) B2 (126 g)4. Preparation of Ink Composition

The pigment dispersion thus above, a deionized water, and 1 g ofSurfynol 465 (ethylene oxide adduct of an acetylenic diol; Air Products)were added sequentially to a beaker with stirring. The combined mixturewas stirred for 3 hours.

Next, the mixture was filtered through an 8-micron membrane filter, suchthat an ink suitable for ink jet printing was obtained.

The content of each component is shown in Table 2 and 3. In Table 2 and3, the abbreviations show the following cosolvents.

gly; glycerol

DEG; diethylene glycol

TEG; triethylene glycol

TeEG; tetraethylene glycol

DEG-mBE; diethylene glycol mono-n-butyl ether

TEG-mBE; triethylene glycol mono-n-butyl ether and

HD; 1,2-hexanediol.

TABLE 2 Pigment Dispersion Water Cosolvents Sample (weight) (weight)(weight) Example Black A1 50 g 27.5 g   Gly (12 g)  1a-1 TEG (5 g) HD (4g) DEG-mBE (0.5 g)   Example Black A1 50 g 30 g Gly (11 g)  2a-1 TeEG (4g) HD (3 g) DEG-mBE (1 g) Example Black B1 50 g 29.5 g   gly (11.5 g)  3a-1 TEG (4 g) HD (3 g) DEG-mBE (1 g) Example Black B1 50 g 26 g Gly(11.5 g)   4a-1 TEG (4 g) HD (5 g) Example Cyan A1 34 g 35 g Gly (14 g) 9a-1 TEG (4 g) DEG-mBE (5 g) Example Cyan B1 32 g 37 g Gly (20 g)  10a-1TeEG (5 g) HD (3 g) DEG-mBE (2 g) Example Yellow A1 40 g 30 g Gly (18g)  15a-1 DEG (7 g) HD (2 g) DEG-mBE (2 g) Example Yellow B1 42 g 26 gGly (21 g)  16a-1 DEG (7 g) DEG-mBE (5 g) Example Magenta A1 45 g 29 ggly (15 g)  17a-1 TEG (5 g) DEG-mBE (5 g) Example Magenta B1 45 g 33 ggly (13 g)  18a-1 TEG (4 g) HD (3 g) DEG-mBE (1 g) Compara- Black C 50 g30 g gly (11 g)  tive (Comparative TEG (4 g) Example Example) HD (3 g)1a-1 DEG-mBE (1 g) Compara- Black D 50 g 29 g gly (12 g)  tive(Comparative TEG (4 g) Example Example) HD (3 g) 2a-1 DEG-mBE (1 g)Compara- Cyan D 32 g 37 g gly (20 g)  tive (Comparative TEG (5 g)Example Example) HD (3 g) 3a-1 DEG-mBE (5 g)

TABLE 3 Pigment Dispersion Water Cosolvents Sample (weight) (weight)(weight) Example Black A2 50 g 27.5 g   Gly (12 g)  1b-1 TeEG (4 g) HD(3 g) TEG-mBE (1 g) Example Black A2 50 g 30 g Gly (12 g)  2b-1 TeEG (5g) HD (2.5 g)   TEG-mBE (1.5 g)   Example Black B2 50 g 29.5 g   gly(12.5 g)   3b-1 TeEG (2 g) DEG (2.5 g)   HD (2.5 g)   DEG-mBE (1 g)Example Black B2 50 g 26 g Gly (13 g)  4b-1 TEG (7 g) HD (1.5 g)  EG-mBE (5 g) Example Cyan A2 34 g 35 g Gly (20 g)  9b-1 TEG (5 g)DEG-mBE (5 g) Example Cyan B2 32 g 37 g Gly (20 g)  10b-1 TEG (5 g) HD(2.5 g)   TEG-mBE (2 g) Example Yellow A2 40 g 30 g Gly (18 g)  15b-1TEG (7 g) HD (2 g) DEG-mBE (3 g) Example Yellow B2 42 g 26 g Gly (21 g) 16b-1 TeEG (2 g) DEG (3 g) DEG-mBE (5 g) Example Magenta A2 45 g 29 ggly (15 g)  17b-1 TEG (5 g) DEG-mBE (5 g) Example Magenta B2 45 g 33 ggly (13 g)  18b-1 TEG (4 g) HD (3 g) TEG-mBE (1 g) Compara- Black C 50 g30 g gly (11 g)  tive (Comparative TEG (4 g) Example Example) HD (3 g)1b-1 DEG-mBE (1 g) Compara- Black D 50 g 29 g gly (12 g)  tive(Comparative TEG (4 g) Example Example) HD (3 g) 2b-1 DEG-mBE (1 g)Compara- Cyan D 32 g 37 g gly (20 g)  tive (Comparative TEG (5 g)Example Example) DEG-mBE (5 g) 3b-15. Evaluation

The ink compositions thus above were evaluated according as to theiroverall reliability and print quality on plain paper.

(1) Continuous Printing Test

The reliability under continuous printing conditions of the above inkswas evaluated as follows. First, the ink was degassed and sealed in aheat-sealable aluminum pack. Next, the ink was loaded into the black-inkprint head of a PM-900C printer (Product Name, Seiko Epson Corporation).A line pattern which uses all of the nozzles was printed initially toestablish that ink was being ejected from all nozzles with gooddirectionality (angular deviation of an ejected ink droplet from anozzle is within about ±0.50 from the normal to the plane of thenozzle). The printing pattern was changed to a 360 dots per inch solidblock pattern that fills an A4 size sheet of paper. This printing speedwas relatively fast such that about 4 pages were completed per minute.The block and line pattern was printed continuously with a printed sheetbeing evaluated every 100 sheets for evidence of loss of directionality,clogged nozzles, or decreases in optical density of the solid blocks(less than 5%). For all of the inks tested, except Comparative Example1, no loss of directionality, no clogged nozzles, and no decreases inoptical density were observed for 10,000 printed sheets, a level whichindicates an acceptable level of reliability. For Comparative Example 1,loss of directionality occurred at less than 5000 sheets.

(2) Long Term Storage Test

The reliability towards long-term storage in the print head of the aboveinks was evaluated as follows. First, the ink was degassed and sealed ina heat-sealable aluminum pack. Next, the ink was loaded into the blackink print head of an MJ-510C printer (Product Name, Seiko EpsonCorporation). A line pattern, which uses all of the nozzles, was printedinitially to establish that ink was being ejected from all nozzles withgood directionality. Next, the ink supply was removed from the printhead, and then the print head was removed from the printer. The uncappedprint head was stored for 4 days at 40° C. in a constant temperatureoven. The print head was reattached to the printer and the ink supplywas reattached to the print head. The cleaning operation of the printerwas executed followed by a line pattern that uses all of the nozzles.The cleaning operation followed by the line pattern was repeated untilall of the nozzles printed with good directionality. For all of the inkstested, except Comparative Example 1, the number of cleaning operationsnecessary for full recovery was less than or equal to 4, a level whichindicates an acceptable level of reliability. For Comparative Example 1,full recovery of all the nozzles was not obtained even after 10 cleaningoperations.

(3) Thermal Cycling Test

The reliability towards two temperature extremes (−30° C. and 60° C.) ofthe above inks was evaluated as follows. First, the ink was degassed andsealed in a 30 mL glass sample bottle. The sample bottle was loaded intoa 60° C. constant temperature oven and stored at that temperaturecondition for 24 hours. The sample was removed from the oven andtransferred to a −30° C. constant temperature refrigerator and stored atthat temperature condition for 24 hours. This two-temperature cycle wasrepeated such that a total of ten cycles was completed. After the lastcycle, the ink was thawed to room temperature, the glass sample bottlewas inverted without shaking, and the bottom of the sample bottle wasexamined for precipitates. For all of the inks tested, exceptComparative Example 1, no precipitates were observable, a level whichindicates an acceptable level of reliability. For Comparative Example 1,precipitate was observed.

(4) Drying Time Test

The drying time of the above inks was evaluated by printing a series ofsolid block patterns and wiping the patterns in 5-second increments. Theprinting was carried out using a PM-930C printer (Product Name, SeikoEpson Corporation) and Xerox 4024 as the paper. For all of the inkstested the drying time was less than 5 seconds, a level that indicatesacceptably fast drying.

(5) Print Quality Test

Print quality, using a PM-930C printer (Product Name, Seiko EpsonCorporation), was evaluated in the following way. A standard set ofJapanese Kanji characters were printed using a Gothic and a Minchou fontat a 4-point character size. The samples were printed at 720 dpi usingXerox 4024 paper as a representative plain paper. The print samples wereevaluated using an optical microscope. The following standards were usedto evaluate the print quality:

A: the Kanji characters were sharp with no filling of interior voidswithin the characters,

B: the Kanji characters were sharp, but there was some filling ofinterior voids within characters with stroke counts greater than about15, and

NG: the Kanji characters were not sharp and there was significantfilling of interior voids within characters with stroke counts greaterthan about 10.

The results of the print quality tests are shown below in Table 4.

TABLE 4 Sample Print Quality Sample Print Quality Example 1a-1 A Example1b-1 A Example 2a-1 A Example 2b-1 A Example 3a-1 A Example 3b-1 AExample 4a-1 A Example 4b-1 A Example 5a-1 A Example 5b-1 A Example 6a-1A Example 6b-1 A Example 7a-1 A Example 7b-1 A Example 8a-1 A Example8b-1 A Example 9a-1 A Example 9b-1 A Example 10a-1 A Example 10b-1 AExample 11a-1 A Example 11b-1 A Example 12a-1 A Example 12b-1 A Example13a-1 A Example 13b-1 A Example 14a-1 A Example 14b-1 A Example 15a-1 AExample 15b-1 A Example 16a-1 A Example 16b-1 A Example 17a-1 A Example17b-1 A Example 18a-1 A Example 18b-1 A Comparative NG Comparative CExample 1a-1 Example 1b-1 Comparative B Comparative B Example 2a-1Example 2b-1 Comparative B Comparative B Example 3a-1 Example 3b-1

As can be seen from the above results in Table 4, all of the inks of thepresent invention showed excellent results for the printing test onplain paper.

6. Preparation of Ink Composition According to the Forth Embodiment

(1) Self-dispersed Pigment

Black Pigment Dispersion A

CAB-O-JET 300 was obtained from the Cabot Corporation as a 15% by weightdispersion.

Black Pigment Dispersion B

Bonjet Black CW-1 was obtained from Orient Chemical as a 15% by weightdispersion.

Black Pigment Dispersion C

A black pigment dispersion was prepared by a method analogous to thatdescribed in Example 2 in WO 01/94476 A2. FW-18 carbon black, obtainedfrom the Degussa Corporation, was used as the pigment starting material.Ozone was generated using a GL-1 ozone generator manufactured by PCIOzone Corporation. A Microfluidizer manufactured by MicrofluidicsCorporation was used to effect dispersive mixing of the pigmentconcurrent with ozone oxidation. The resulting dispersion was purifiedby ultrafiltration using a Pellicon Laboratory System obtained from theMillipore Corporation. The final concentration of the dispersion was 15%by weight. The average particle size of the dispersion, as measuredusing a Honeywell Microtrac® UPA 150 particle size analyzer, was 98nanometers.

Yellow Pigment Dispersion

A yellow pigment dispersion was prepared by the following general methodwhich is a modification of Treatment 2 as described in EP 0 894 835 B1.Dispersive mixing was carried out concurrent with the pigment surfacereaction as described in WO 01/94476 A2. 20 parts of Novoperm YellowP-HG, obtained from the Clariant Corporation, was used as the pigmentstarting material. The pigment was suspended and then dispersed in 550parts of pyridine using a Microfluidizer manufactured by MicrofluidicsCorporation. Next, the mixture was heated to reflux and awater-containing distillation forerun was distilled off and discarded(about 10% of the total solvent volume). In a closed reaction systemunder an dry argon atmosphere, 10 parts of liquid sulfur trioxide wereadded gradually to the pigment dispersion in pyridine while heating themixture at 110° C. During the addition of sulfur trioxide, the mixturewas circulated through the Microfluidizer in order to effect dispersivemixing of the pigment concurrent with sulfonation. The addition anddispersive mixing processes were carried out continuously for a periodof 6 hours. After cooling to room temperature the mixture was pouredslowly into 5000 parts of an ice slurry while stirring the combinedmixture vigorously. The mixture was transferred to a rotary evaporatorand most of the pyridine was removed as an aqueous azeotrope such thatan aqueous dispersion remained. While stirring the aqueous dispersion, a5% by weight solution of potassium hydroxide was added dropwise untilthe pH of the dispersion was about 9. Next, the dispersion was purifiedand concentrated by ultrafiltration using a Pellicon Laboratory Systemobtained from the Millipore Corporation. The final concentration of thedispersion was 13% by weight. The average particle size of thedispersion was 110 nanometers.

Magenta Pigment Dispersion

A magenta pigment dispersion was prepared by a general method nearly thesame as that described above for the yellow pigment dispersion. 20 partsof Fastogen Super Red, obtained from Dainippon Ink, was used instead ofthe yellow pigment. The addition and dispersive mixing processes werecarried out continuously for a period of 10 hours. The finalconcentration of the dispersion was 12% by weight. The average particlesize of the dispersion was 140 nanometers.

Cyan Pigment Dispersion

A cyan pigment dispersion was prepared by a general method nearly thesame as that described above for the yellow pigment dispersion. 20 partsof Toner Cyan B, obtained from the Clariant Corporation, was usedinstead of the yellow pigment. The addition and dispersive mixingprocesses were carried out continuously for a period of 5 hours. Thefinal concentration of the dispersion was 15% by weight. The averageparticle size of the dispersion was 95 nanometers.

(2) Preparation of Ink Composition

The pigment dispersion avobe, a deionized water, the polyuronic acidderivatives obtained above (A1 to B2), cosolvents, and 2 g of Surfynol465 (ethylene oxide adduct of an acetylenic diol; Air Products) wereadded sequentially to a glass beaker with stirring. The combined mixturewas stirred for one hour. While stirring the mixture gently using anoverhead stirrer, the combined mixture was subjected to ultrasonicationin an ultrasonication bath for 30 minutes. Next, the mixture wasfiltered through an 8-micron membrane filter, such that an ink suitablefor ink jet printing was obtained.

The composition ratio of each component was shown in Table 5 and 6 (theunits for the parenthetically listed quantities are grams).

TABLE 5 Poly- uronic Pigment acid Dispersion Water deriv- CosolventsSample (weight) (weight) ative (weight) Example Black A 94 g 40 g A1 gly(22 g)  1a-2 2P (4 g) TEG (5 g) DEG- (1 g) mBE HD (6 g) Example Black A94 g 40 g B1 gly (21 g)  2a-2 2P (5 g) DEG (5 g) TEG- (2 g) mBE HD (6 g)Example Black B 94 g 38 g A1 gly (24 g)  3a-2 2P (4 g) TeEG (5 g) TEG-(2 g) mBE HD (6 g) Example Black B 94 g 38 g B1 gly (24 g)  4a-2 2P (4g) TeEG (5 g) TEG- (2 g) mBE HD (6 g) Example Black C 87 g 48 g A1 gly(21 g)  5a-2 2P (4 g) TEG (5 g) TEG- (2 g) mBE HD (6 g) Example Black C87 g 48 g B1 gly (21 g)  6a-2 2P (4 g) TEG (5 g) TEG- (2 g) mBE HD (6 g)Example Yellow 100 g  26 g A1 gly (27 g)  7a-2 2P (4 g) TEG (7 g) TEG-(2 g) mBE HD (6 g) Example Yellow 100 g  26 g B1 gly (28 g)  8a-2 2P (4g) TeEG (6 g) DEG- (4 g) mBE HD (6 g) Example Magenta 92 g 41 g A1 gly(25 g)  9a-2 2P (3 g) TeEG (5 g) TEG- (4 g) mBE HD (6 g) Example Magenta92 g 41 g B1 gly (25 g)  10a-2 2P (3 g) TeEG (5 g) TEG- (4 g) mBE HD (6g) Example Cyan 54 g 72 g A1 gly (32 g)  11a-2 2P (5 g) DEG (10 g)  TEG-(4 g) mBE HD (6 g) Example Cyan 54 g 72 g B1 gly (30 g)  12a-2 2P (5 g)DEG (10 g)  TEG- (4 g) mBE HD (6 g) Compar- Black A 94 g 61 g — gly (25g)  ative 2P (5 g) Example TEG (5 g) 1a-2 DEG- (2 g) mBE HD (6 g)Compar- Black B 94 g 59 g — gly (27 g)  ative 2P (5 g) Example TeEG (5g) 2a-2 TEG- (2 g) mBE HD (6 g) Compar- Black C 94 g 69 g — gly (24 g) ative 2P (5 g) Example TEG (5 g) 3a-2 TEG- (2 g) mBE HD (6 g) Compar-Yellow 100 g  46 g — gly (31 g)  ative 2P (4 g) Example TeEG (7 g) 4a-2DEG- (4 g) mBE HD (6 g) Compar- Magenta 92 g 59 g — gly (28 g)  ative 2P(3 g) Example TeEG (6 g) 5a-2 TEG- (4 g) mBE HD (6 g) Compar- Cyan 54 g85 g — gly (34 g)  ative 2P (5 g) Example DEG (10 g)  6a-2 TEG- (4 g)mBE HD (6 g)

TABLE 6 Poly- uronic Pigment acid Dispersion Water deriv- CosolventsSample (weight) (weight) ative (weight) Example Black A 94 g 39 g A2 gly(25 g)  1b-2 2P (6 g) TeEG (5 g) TEG-mBE (4 g) HD (5 g) Example Black A94 g 37 g B2 gly (26 g)  2b-2 2P (6 g) TEG (5 g) TEG-mBE (4 g) HD (5 g)Example Black B 94 g 40 g A2 gly (24 g)  3b-2 2P (5 g) TeEG (5 g)DEG-mBE (5 g) HD (5 g) Example Black B 94 g 38 g B2 gly (25 g)  4b-2 2P(5 g) TeEG (5 g) DEG-mBE (5 g) HD (5 g) Example Black C 87 g 39 g A2 gly(26 g)  5b-2 2P (5 g) DEG (7 g) TEG-mBE (6 g) HD (4 g) Example Black C87 g 37 g B2 gly (27 g)  6b-2 2P (4 g) DEG (7 g) TEG-mBE (6 g) HD (4 g)Example Yellow 92 g 17 g A2 gly (27 g)  7b-2 2P (4 g) TeEG (5 g) DEG-mBE(6 g) HD (4 g) Example Yellow 92 g 15 g B2 gly (28 g)  8b-2 2P (3 g)TeEG (5 g) DEG-mBE (6 g) HD (6 g) Example Magenta 92 g 36 g A2 gly (21g)  9b-2 2P (3 g) DEG (5 g) TEG-mBE (4 g) HD (7 g) Example Magenta 92 g34 g B2 gly (22 g)  10b-2 2P (3 g) DEG (5 g) TEG-mBE (4 g) HD (7 g)Example Cyan 48 g 59 g A2 gly (32 g)  11b-2 2P (4 g) TEG (10 g)  TEG-mBE(4 g) HD (6 g) Example Cyan 48 g 58 g B2 gly (32 g)  12b-2 2P (4 g) TEG(10 g)  TEG-mBE (4 g) HD (6 g) Compar- Black A 94 g 56 g — gly (28 g) ative 2P (6 g) Example TeEG (5 g) 1b-2 TEG-mBE (4 g) HD (5 g) Compar-Black B 94 g 54 g — gly (30 g)  ative 2P (5 g) Example TeEG (5 g) 2b-2DEG-mBE (5 g) HD (5 g) Compar- Black C 87 g 61 g — gly (29 g)  ative 2P(4 g) Example DEG (7 g) 3b-2 TEG-mBE (6 g) HD (4 g) Compar- Yellow 92 g55 g — gly (30 g)  ative 2P (5 g) Example TeEG (5 g) 4b-2 DEG-mBE (6 g)HD (6 g) Compar- Magenta 92 g 63 g — gly (24 g)  ative 2P (4 g) ExampleTeEG (5 g) 5b-2 TEG-mBE (4 g) HD (7 g) Compar- Cyan 48 g 91 g — gly (35g)  ative 2P (3 g) Example TEG (10 g)  6b-2 TEG-mBE (4 g) HD (6 g)

In addition to the above ink formulations, four inks based onconventional pigment dispersions were evaluated. As Comparative Example7, the black ink of Epson Part #T034120 was used. As Comparative Example8, the yellow ink of Epson Part #T034420 was used. As ComparativeExample 9, the magenta ink of Epson Part #T034320 was used. AsComparative Example 10, the cyan ink of Epson Part #T034220 was used.

(3) Evaluation

The above inks were evaluated as described below.

(i) Continuous Printing Test

The reliability under continuous printing conditions of the above inkswas evaluated as follows. First, the ink was degassed and sealed in aheat-sealable aluminum pack. Next, the ink was loaded into the black-inkprint head of a PM-900C printer (Product Name, Seiko Epson Corporation).A line pattern which uses all of the nozzles was printed initially toestablish that ink was being ejected from all nozzles with gooddirectionality (angular deviation of an ejected ink droplet from anozzle is within about ±0.50 from the normal to the plane of thenozzle). The printing pattern was changed to a 360 dots per inch solidblock pattern that fills an A4 size sheet of paper. This printing speedwas relatively fast such that about 4 pages were completed per minute.The block and line pattern was printed continuously with a printed sheetbeing evaluated every 100 sheets for evidence of loss of directionality,clogged nozzles, or decreases in optical density of the solid blocks(less than 5%). For all of the inks tested, no loss of directionality,no clogged nozzles, and no decreases in optical density were observedfor 10,000 printed sheets, a level which indicates an acceptable levelof reliability.

(ii) Long Term Storage Test

The reliability towards long-term storage in the print head of the aboveinks was evaluated as follows. First, the ink was degassed and sealed ina heat-sealable aluminum pack. Next, the ink was loaded into the blackink print head of an MJ-510C printer (Product Name, Seiko EpsonCorporation). A line pattern, which uses all of the nozzles, was printedinitially to establish that ink was being ejected from all nozzles withgood directionality. Next, the ink supply was removed from the printhead, and then the print head was removed from the printer. The uncappedprint head was stored for 4 days at 40° C. in a constant temperatureoven. The print head was reattached to the printer and the ink supplywas reattached to the print head. The cleaning operation of the printerwas executed followed by a line pattern that uses all of the nozzles.The cleaning operation followed by the line pattern was repeated untilall of the nozzles printed with good directionality. For all of the inkstested, the number of cleaning operations necessary for full recoverywas less than or equal to 4, a level which indicates an acceptable levelof reliability.

(iii) Thermal Cycling Test

The reliability towards two temperature extremes (−30° C. and 60° C.) ofthe above inks was evaluated as follows. First, the ink was degassed andsealed in a 30 mL glass sample bottle. The sample bottle was loaded intoa 60° C. constant temperature oven and stored at that temperaturecondition for 24 hours. The sample was removed from the oven andtransferred to a −30° C. constant temperature refrigerator and stored atthat temperature condition for 24 hours. This two-temperature cycle wasrepeated such that a total of ten cycles was completed. After the lastcycle, the ink was thawed to room temperature, the glass sample bottlewas inverted without shaking, and the bottom of the sample bottle wasexamined for precipitates. For all of the inks tested, no precipitateswere observable, a level which indicates an acceptable level ofreliability.

(iv) Print Quality: Plain Paper Text Sharpness

Print quality, in terms of plain paper optical density, was evaluated inthe following way. For all ink samples, a fully saturated standard colorpatch was printed on Xerox 4024 paper at 720 dpi using a Stylus Color980 printer (Product Name, Seiko Epson Corporation). After allowing theprinted sample to dry at ambient temperature overnight, the opticaldensity of the printed patch was evaluated using a Gretag-MacbethSpectrolino instrument equipped with a Spectroscan table unit. For blackinks, the following standards were used to evaluate the print quality interms of plain paper optical density:

A: the optical density value was greater than 1.3,

B: the optical density value was greater than 1.2 but less than 1.3,

C: the optical density value was greater than 1.1 but less than 1.2,

D: the optical density value was greater than 1.0 but less than 1.1, and

F: the optical density value was less than 1.0.

For yellow, magenta, and cyan inks, the following standards were used toevaluate the print quality in terms of plain paper optical density:

A: the optical density value was greater than 1.2,

B: the optical density value was greater than 1.1 but less than 1.2,

C: the optical density value was greater than 1.0 but less than 1.1,

D: the optical density value was greater than 0.9 but less than 1.0, and

F: the optical density value was less than 0.9.

The results of this print quality test are shown below in Table 7 and 8.

(v) Print Quality: Plain Paper Text Sharpness

Print quality, in terms of text sharpness on plain paper, was evaluatedin the following way. For all ink samples, a standard set of JapaneseKanji characters was printed using both Gothic and Minchou fonts at a6-point character size. The samples were printed at 720 dpi using Xerox4024 paper, as a representative plain paper, using a Stylus Color 980printer (Product Name, Seiko Epson Corporation). The print samples wereevaluated using an optical microscope. The following standards were usedto evaluate the print quality:

A: the Kanji characters were sharp with no filling of interior voidswithin the characters,

B: the Kanji characters were sharp, but there was some filling ofinterior voids within characters with stroke counts greater than about15, and

C: the Kanji characters were not sharp and there was significant fillingof interior voids within characters with stroke counts greater thanabout 10.

The results of this print quality test are shown below in Table 7 and 8.

TABLE 7 Plain Paper Specialty Media OD Text OD Lustrous- Sample ValueSharpness Value ness Adhesion Example 1a-2 A A A A A Example 2a-2 A A AA A Example 3a-2 A A A A A Example 4a-2 A A A A A Example 5a-2 A A A A AExample 6a-2 A A A A A Example 7a-2 A A A A A Example 8a-2 A A A A AExample 9a-2 A A A A A Example 10a-2 A A A A A Example 11a-2 A A A A AExample 12a-2 A A A A A Comparative A B B C C Example 1a-2 Comparative AB B C C Example 2a-2 Comparative A B B C C Example 3a-2 Comparative A BB C C Example 4a-2 Comparative A B B C C Example 5a-2 Comparative A B BC C Example 6a-2 Comparative F C A A A Example 7a-2 Comparative D C A AA Example 8a-2 Comparative F C A A A Example 9a-2 Comparative D C A A AExample 10a-2

TABLE 8 Plain Paper Specialty Media OD Text OD Lustrous- Sample ValueSharpness Value ness Adhesion Example 1b-2 A A A A A Example 2b-2 A A AA A Example 3b-2 A A A A A Example 4b-2 A A A A A Example 5b-2 A A A A AExample 6b-2 A A A A A Example 7b-2 A A A A A Example 8b-2 A A A A AExample 9b-2 A A A A A Example 10b-2 A A A A A Example 11b-2 A A A A AExample 12b-2 A A A A A Comparative A B B C C Example 1b-2 Comparative AB B C C Example 2b-2 Comparative A B B C C Example 3b-2 Comparative A BB C C Example 4b-2 Comparative A B B C C Example 5b-2 Comparative A B BC C Example 6b-2

(vi) Print Quality: Specialty Media Optical Density Test

Print quality, in terms of specialty media optical density, wasevaluated in the following way. For all ink samples, a fully saturatedstandard color patch was printed on Epson Premium Glossy Photo Paper atthe default setting for that medium using a Stylus Color 980 printer(Product Name, Seiko Epson Corporation). After allowing the printedsample to dry at ambient temperature overnight, the optical density ofthe printed patch was evaluated using a Gretag-Macbeth Spectrolinoinstrument equipped with a Spectroscan table unit. The followingstandards were used to evaluate the print quality in terms of specialtymedia optical density:

A: the optical density value was greater than 2.0,

B: the optical density value was greater than 1.9 but less than 2.0,

C: the optical density value was greater than 1.8 but less than 1.9,

D: the optical density value was greater than 1.7 but less than 1.8, and

F: the optical density value was less than 1.7.

The results of this print quality test are shown below in Table 7 and 8.

(vii) Print Quality: Specialty Media Lustrousness Test

Print quality, in terms of specialty media that exhibit lustrousness,was evaluated in the following way. For all ink samples, a singleindividual sample was evaluated as one component of a four-color(Yellow-Magenta-Cyan-Black) ink set. For the three remainingcomplementary reference colors of the four-color evaluation set, theappropriate three inks were selected from the set of inks in ComparativeExamples 7 through 10. As the reference sample for this print qualitytest, all four of the inks in Comparative Examples 7 through 10 wereused. A standard photographic portrait of a brunette model was printedon Epson Premium Glossy Photo Paper at the default setting for thatmedium using a Stylus Color 980 (Product Name, Seiko Epson Corporation).All printed samples were set aside to dry at ambient temperatureovernight. The following standards were used to evaluate the printquality in terms of specialty media lustrousness:

A: in comparison to the reference sample, there were no distinguishabledifferences in lustrousness across the whole photographic image,

B: in comparison to the reference sample, there were slight differencesin lustrousness across the whole photographic image. For evaluated blackand cyan inks, these differences were most noticeable within regions ofthe model's hair. For evaluated magenta and yellow inks, thesedifferences were most noticeable within regions of the model's face.

C: in comparison to the reference sample, there were large differencesin lustrousness across the whole photographic image. For evaluated blackand cyan inks, these differences were most noticeable within regions ofthe model's hair. For evaluated magenta and yellow inks, thesedifferences were most noticeable within regions of the model's face.

The results of this print quality test are shown below in Table 7 and 8.

(viii) Print Quality: Specialty Media Adhesion Test

Print quality, in terms of adhesion on specialty media, was evaluated inthe following way. For all ink samples, multiple lines of a standardtext sample at a 14-point character size was printed on Epson PhotoPaper at the default setting for that medium using a Stylus Color 980printer (Product Name, Seiko Epson Corporation). After allowing theprinted sample to dry at ambient temperature overnight, a fluorescenthighlighting pen (Zebra Zazzle Fluorescent Highlighter, Zebra PenCompany) was marked over a 3 centimeter strip of text at a pressure of300 grams. A yellow highlighting pen was used for black, cyan, andmagenta text samples. A pink highlighting pen was used for yellow textsamples. The following standards were used to evaluate the print qualityin terms of adhesion on specialty media:

A: there was no streaking of the printed text images into thehighlighted ink;

B: there was slight streaking of the printed text images into thehighlighted ink;

C: there was considerable streaking of the printed text images into thehighlighted ink.

The results of this print quality test are shown below in Table 7 and 8.

As can be seen from the above results in Table 7 and 8, all of the inksof the present invention showed excellent results for the all of theprint quality tests.

1. A polyuronic acid derivative comprising glyceryl poly(oxypropylene)triamine and polyuronic acids which are attached by reductivelyamination, through reducing termini of the polyuronic acids, to theglyceryl poly(oxypropylene) triamine.
 2. The polyuronic acid derivativeaccording to claim 1, wherein one polyuronic acid is attached byreductively amination, through a reducing terminus of the polyuronicacid, to the glyceryl poly(oxypropylene) triamine which is representedby the general formula:

wherein the average value of the sum, x+y+z, is greater than or equal to10 and less than or equal to
 150. 3. The polyuronic acid derivativeaccording to claim 2, wherein the average value of the sum, x+y+z, inthe glyceryl poly(oxypropylene) triamine represented by the generalformula is greater than or equal to 10 and less than or equal to
 100. 4.The polyuronic acid derivative according to claim 1, wherein two to sixpolyuronic acids are attached by reductively amination, through reducingtermini of the polyuronic acid, to the glyceryl poly(oxypropylene)triamine which is represented by the general formula:

wherein the average value of the sum, x+y+z, is greater than or equal to30 and less than or equal to
 250. 5. The polyuronic acid derivativeaccording to claim 4, wherein the average value of the sum, x+y+z, inthe glyceryl poly(oxypropylene) triamine represented by the generalformula is greater than or equal to 30 and less than or equal to
 120. 6.The polyuronic acid derivative according to claim 1, wherein thepolyuronic acid is composed primarily of 1,4-linkedpoly-(a-D-galacturonic acid) or 1,4-linked poly-(a-L-guluronic acid). 7.The polyuronic acid derivative according to claim 1, wherein the numberaverage molecular weight of the polyuronic acid segment is greater thanor equal to
 700. 8. A pigment dispersant comprising the polyuronic acidderivative according to claim
 1. 9. A pigment dispersed aqueous inkcomposition comprising water as the principal solvent, a pigment, andthe pigment dispersant according to claim
 8. 10. The pigment dispersedaqueous ink composition according to claim 9, wherein said inkcomposition contains 0.1 to 20% pigment, 0.1 to 10% pigment dispersant,and 70 to 99.8% aqueous carrier medium.
 11. An aqueous ink compositioncomprising water as the principal solvent, a self-dispersed pigment, andthe polyuronic acid derivative according to claim
 1. 12. The aqueous inkcomposition according to claim 11, wherein the ink composition contains0.1 to 20% self-dispersed pigment, 0.1 to 10% polyuronic acidderivetive, and 70 to 99.8% aqueous carrier medium.
 13. The aqueous inkcomposition according to claim 10, wherein the polyuronic acid segmentin the polyuronic acid derivative is neutralized with a neutralizingagent selected from the group consisting of organic bases,alkanolamines, alkali metal hydroxides, and mixtures thereof.
 14. Aprinting method comprising the step of depositing the ink compositionaccording to claim 9 onto a recording medium.
 15. An ink jet recordingmethod comprising the steps of ejecting and depositing droplets of theink composition according to claim 9 onto a recording medium.
 16. Arecord produced by the method according to claim 14.